A word processing software is quite complex, but you see most of them are about formatting, layout, design, or adjusting the elements of text decoration, rather than functional to help you getting your task of writing an academic document. This is a design choice, so remember that while a standard word processing software is great for writing memos and simple documents with nice style and formatting, they are not necessarily functional to write complex academic documents with ease so that you can insert formulae, images, tables, and citations. That said, you can achieve all of these in a standard word processor but it takes more work to do them. I have talked about academic writing, so this is a good jumping point to learn about what makes academic writing academic.

Elements of academic writing

In academic writing, your aim is to create meaning, and rewrite till the meaning becomes clear to you and to your target audience \cite{Cameron2009}. Using words, you have to create meaning that you can easily convey to your readers, and this process is iterative. So, you need a tool that can adjust to your rewriting processes rather than you create something once and adjust with minor 'tweaking' of the appearance. For rewriting a document, you need to be:

How to write paragraphs: discussion of practices

Composing a paragraph in Authorea is no different from composing a paragraph of text in any other word processor (Word/typewriter/even paper). You find an open space and start writing. However, we still need to discuss what to write and how to write the text. Ideally a paragraph is about 100-120 words long, so for an assignment of about 1500 words, plan on having about 15-20 paragraphs and decide where they will go. One way to make sure you are on track is to first set up an outline of your paper.
Start with an outline and keep in mind that you can change the outline as you go. If you are writing a research proposal, you have two ways about it. You propose on your own. For example, I want to propose a research on developing polygenic risk scores for ambulatory care sensitive conditions (a list of five diseases where care provided in primary care setting can prevent or delay hospitalised care), so I will have to set up the rationale and the methods all by myself. At other times, potential funders would like you to focus on a particular topic of their interest. Usually, in such situations, you will get initial ideas and scope of the problem from them. Use these to build your outlines. 
When you build an outline, keep things simple. Start with single sentences and phrases. Stick to two levels of headings (H1 and H2 on Authorea). For example, if you want to write a journal article, you will learn that the reporting format of IMRAD (Introduction, Methods, Results, And, Discussion) is a preferred pattern of writing that editors would like you to adopt \cite{wu2011improving}. Now, although this sounds fine in principle, it does not mean that you will write your research paper, you will start with introduction and end with discussion. Some people do. Many people would prefer to write the methods and results first, then the discussion section, finally the introduction and end up with the abstract. So while this is a personal preference, keeping the introduction, methods, results, and discussion as first level headers and then within them other header levels to organise the paper helps.  Once you set up the organisation of the paper using the headers, then it is time to fill in the paragraph space.
Paragraphs are nested within the headings. By 'nested', I mean that paragraphs are the children of the headers and the headers contain a space that you will fill. You can move around the headers but it helps to have dedicated spaces within which you write the paragraphs. Each paragraph is a unit of your idea that then are connected with each other to form the paper. Each paragraph also contains sentences that make up the thought that goes into the paragraph. So how do you organise the sentences within the paragraphs?
Start each paragraph with a topic sentence. April Klazema (2014) wrote a blog for Udemy where she has provided guidance about writing topic sentences, worth visiting. If you follow the dictum of writing paragraphs such that you 'state what you want to state, then you state it, and then you state what you just stated', the topic sentence is the part of 'state what you want to state'. Then continue with justifiying or explaining the topic sentence in the middle of the paragraph. Finally, end the paragraph with a summary sentence. In the summary sentence you paraphrase the message of the paragraph, and then lead to the next paragraph. If your last sentence happens to be in a paragraph that is the last paragraph in the last section of the paper, then that would be the last sentence of the paper. That sentence should capture the essence of the paper and where you are heading next. So a topic sentence sets the tone of your message, starting with the first topic sentence of the first paragraph of the paper or proposal, but what about the general structure?
Williams and Bizup (2010) in their classic book, "Style: lessons towards clarity and grace" advise that you should start with known facts or simple facts, and add complexity as the paragraphs extend towards the end of the section \cite{williams2010style}. The same goes for writing sentences in a single paragraph. Start with what you know or expect your readers to know, or start with a sentence that captures what you wrote in the previous paragraph but also signal a new idea coming connected to the previous paragraph. Then continue with the rest of the paragraph. At each stage remember your constraints: (a) you can add facts to justify your positions, and (b) you can explain phenomena. You are not allowed to express your personal opinions in an academic paper, and everything you write must be backed up by citations. In summary, start with simple known facts or facts already stated, and then continue to build your arguments. This also means you write with the structure of 'subject - verb- object' and use nouns and verbs. Avoid adjectives and stay away from using adverbs.
So to summarise:
But as you will argue, academic writing is more than writing paragraphs. We will also need to use tables and graphs/figures, lists, and citations. In the next sections, I will outline how you can do them in Authorea.  Start with the easiest option: inserting lists, then inserting figures, how to insert tables, and finally, how to insert citations in Authorea. 

How to insert lists in Authorea

If you want to insert a list of items in Authorea, you have two choices: (1) bullet point lists and (2) numbered lists. Use bullet point lists if you think all items in the list are equivalent, and use a numbered list if you think that there is a hierarchical order in which the list items are enumerated. If you want to insert a list where the elements do not have any inherent rank order, then use a bulleted or unordered list. On the other hand, if you want to insert a list that has an inherent order of elements in the list, use an ordered list. For example, let's say you are writing a proposal where you want to indicate the elements that you will include in a questionnaire. If these are for instance, 'age', 'sex', 'socioeconomic status', indicate them in an unordered list as such:
In order to use an unordered list in Authorea, click on the unordered list icon and insert the items on the list. 
You will insert an ordered or numbered list if you wanted to list items that have an inherent order in them. For example, if you are writing a proposal and you want to include the steps of data analysis in the methods section, you will include an ordered list or numbered list thus:
  1. Step 1: I will obtain the data
  2. Step 2: I will pre-process the data
  3. Step 3: I will tabulate individual variables
  4. Step 4: I will examine cross-tabulation of variables
  5. Step 5: I will set up multivariable models
As before, you select the numbered list icon from the 'bread crumb' on the top of the Authorea bar and you will insert the items: insert the first item, then press enter and continue to insert items. The next element in order is insertion of tables and figures. 

How to insert tables in Authorea

You can insert tables in Authorea in two ways:
To upload a csv file, you will need to have a CSV formatted table in your computer. Then click on the table icon in the breadcrumb at the top of Authorea, select the table, and Authorea will insert it. For example, the following table was inserted this way: