References can be imported from websites, library databases or PDF documents. The different ways to get references into Mendeley are outlined below.
This works well for single articles on a web page and for some databases. To install the Web importer either:
From Mendeley web: install from Mendeley home page OR
From Mendeley desktop: Install the Web Importer from the Tools menu.
When you locate an article you wish to put into Mendeley, click the Save to Mendeley button (Safari/IE) or Mendeley icon 
(Chrome) to save.
There are mixed results using this with Library databases. It works well with ScienceDirect and can be used with Google Scholar but is not very successful for MultiSearch or EBSCO databases. To save references from these databases, see the below instructions on importing from another file format.
Mendeley offers great flexibility for importing pdfs. Either:
Drag and drop PDFs into your Library
Import pdfs - Click Add – Import document (web version) or Add Files (Desktop)
Set up a Watch folder to enable Mendeley to import a pdf automatically. Go to Add files (desktop) – Watched Folder and select a folder. When you add a pdf to the folder, Mendeley will automatically add it to your Library.
Mendeley will extract the citation details to create the reference and link the fulltext pdf. Depending on the pdf, sometimes you need to manually edit the details if information is missing.
Desktop version: Click Add Files - Add Entry Manually
Web version: Click Add - New Manual Entry
From Mendeley desktop click File - Import - select the RIS file you wish to import.
This method works well to save multiple items from MultiSearch or EBSCO databases into Mendeley. Simply ensure that your file of references exports as a .ris file or .xml file.
MultiSearch instructions:
EBSCO instructions: