Mendeley Official Website
Mendeley Quick Start (Taubman Health Sciences Library, UMichigan)
Installing the plugin for MIcrosoft Word:
UMaine does not allow downloads from the Microsoft App Store, so if you are using Microsoft Office 365 through the University, you will not be able to use Mendeley Cite. However, you will be able to install a plugin that gives you access to your Mendeley citations.
Here's how: With Office completely closed, open your Mendeley installation, and in choose "Tools". Click on "Install MS Word Plugin" in the pulldown. Then, open Word, choose the References tab, and you'll see that Mendeley is installed.
Also, under Tools, install the Web Importer.