Sync your Library with your Mendeley Web account.
Syncing allows you to share your reference data with all your Mendeley accounts (Mendeley Reference Manager, Mendeley Desktop, and Mendeley Mobile Apps). If you want to have the desktop application installed on more than one computer, syncing through the Mendeley Web account will keep the information up-to-date on all of your machines. Syncing is done in Mendeley Desktop.
You can also use the web importer browser extension to add papers to your Mendeley account. This tool is not supported by every database or journal collection. Sometimes it will work with a list of results and other times it may work with a single article.
The easiest way to add papers to Mendeley is to drag and drop PDFs from your files. You may also use the Add Files option and select one or more PDFs from your files. Mendeley will attempt to extract metadata from the PDF to create a citation – author, title, year, volume, etc.
1. Drag and Drop PDFs
Drag PDF from your desktop or folder on your computer to the center pane of Mendeley Desktop or Mendeley Reference Manager.
2. Use the Add Files icon on the toolbar in Mendeley Desktop (on your computer) or in Mendeley Reference Manager (online).
Click the Add Files icon and select the file(s) from your computer. You can input an entry manually, add PDFs, or import an citation from another database format (Endnote (.xml), RIS (.ris), BibTeX (.bib)).
Mendeley Desktop (Mac): 
Mendeley Desktop (Windows) 
Mendeley Referenece Manager (online) 
IMPORTANT: Remember that a citation tool is only as good as the person using it. Always double check the information (author, article title, publication type...) that Mendeley extracts from your document, it can be wrong. Mendeley usually prompts you to confirm the information it imports:
Creating a Watched Folder. When a PDF (or mutiple PDFs) are dropped into a Watched Folder, Mendeley will automatically ingest them. Set up the Watched folder in the Options (PC) or Preferences (Mac) menu item.
