Zotero is a free, open-source citation management tool which allows you to easily collect, manage, cite and share research sources.
To get started you will need to:
1) Download the Zotero Desktop Application available for Windows, Mac and Linux.
2) Once you've downloaded Zotero, you'll also want to download the Zotero Connector to add content with a single click. The Zotero Connector is available for Chrome, Firefox and Safari. If you plan to access items from a mobile device, you may want to download the Zotero Bookmarklet which will allow you to save to your online Zotero library.
3) If you plan to use Microsoft Word or LibreOffice, open Zotero and install the citation add-in by selecting Edit > Preferences choosing the Cite option and selecting the Word Processors tab. Select the add-in you wish to install.

If you've installed the Zotero Connector for Chrome or Firefox and have the Zotero program installed, a Zotero menu option will automatically appear in Google Docs.

4) Configure your citation style from within Zotero by selecting Edit > Preferences and choosing the Cite option. You may choose from one of the built-in options or you can choose from over 8,000 additional styles which can be found in the Zotero Style Repository.

5) Sign up for an online account so you can synchronize and backup your work across devices, join groups and access your content online.
That's it! For more information you may want to visit the Adding Content to Zotero or Generating Citations and Bibliographies sections of this guide.