Click the image above (or this link https://www.zotero.org/) and:
What Zotero Does
Zotero (pronounced "zoh-TAIR-oh") is an application that collects, manages, and cites research sources. It's easy to use, connects with your web browser to download sources, and best of all it's free.
Zotero allows you to attach PDFs, notes and images to your citations, organize them into collections for different projects, and create bibliographies.
The screencast below gives you a walk-through on downloading it and what it can do.