Watch this 2 minute video to learn how to import resources into Mendeley:
A Few Important Highlights:
You can review the different ways to import files that you already have here and how to import files from the web here.
Does it seem like you are missing files? Has your teammate told you that they added a paper to the Mendeley library, but you can't find it?
It's likely that your library is not synced! If working in the web version of Mendeley, you can simply refresh your browser. If you are working in Mendeley Desktop though, you have to hit the "Sync" button in the top ribbon.
When in doubt, sync your library!