Citation managers, like Mendeley, EndNote, RefWorks, and Zotero, help you to gather all your sources and citations into your own mini-database. Mendeley calls this database your Library. You can search and organize your Library citations. Mendeley will also communicate with your word processing program, so you can insert citations into your papers in a style, such as APA or MLA. You can also link PDF files to entries in your Library, making it easier to sort through and view your full text articles. You can catch and merge duplicates, and correct errors.
You can download versions for Mac, iOS, PC, and Linux from https://www.mendeley.com/. Then you have some further steps:
These steps are covered in either the video below, or the videos on the "How To" tab.