First, export a .bib file from your reference manager, or create a .bib file manually. Then, upload the .bib file via the files menu. You can also import .bib files via the direct Mendeley or Zotero integration on the premium plans.

Once your bibliography file has been uploaded, there are a number of bibliography packages which can be used to display the relevant entries in your document (as you cite them). As an example, we often use the natbib package, and the commands for natbib look like:

...
\usepackage{natbib}
...
\begin{document}
...
\bibliographystyle{plainnat}
\bibliography{name-of-your-bib-file-here}
\end{document}


You can also edit the bib file directly via the files menu. For additional information on adding a bibliography to your document, see Part 2 of our Intro to LaTeX course or check out the LaTeX Wikibook.