Anyway, you can add citations and references to Authorea in several ways:
  1. Directing searching from Authorea and by adding the citation
  2. Adding a bibtex entry in the citation window by searching on Google Scholar
  3. Using a citation manager such as Mendeley or Zotero
  4. Uploading a bibtex file in the file space (this can be time saving but complex)

Search directly from Authorea and add citation: for this, take the following steps:

Step 1. Click where you want to insert the citation and click on the 'cite' button at the breadcrumb. You will see something like as follows: