Check out the main Get Organized page for an explanation of what Zotero and why you should consider using it.
How do I download Zotero?
To download either the Zotero Firefox extension or the standalone version, simply click on the "download" button (it's hard to miss) on the Zotero home page.
Next, choose the version of Zotero compatible with your browser and/or operating system. If you are downloading the standalone version, choose among the Windows, Mac, or Linux versions, and then download the "connectors" for Chrome or Safari (if you are using either browser). The latest release of Zotero (as of 07/25/12) is version 3.0.8.
How do I register for a Zotero account and why should I?
Registering for an online account is not necessary in order to use Zotero; however, your registering enables you to sync your library and gain access to it from any computer. It also allows you to participate in groups or post to the support forums
To register for an online account, navigate to www.zotero.org and click on the "register" link in the upper right-hand corner of the page:
Then simply fill out your personal information, submit, and begin using your new account.
How do I download Zotero plugins for my word-processing program? What's the advantage of doing so?
Zotero for Firefox provides plugins for use with Microsoft Word (for Windows or Mac), LibreOffice, OpenOffice, and NeoOffice. These plugins allow one directly to add citations and generate dynamic bibliographies (drawn from your Zotero account) within a word-processing program.
To download the plugins, navigate to Zotero's word-processor plugin installation page and choose the appropriate plugin. Restart both Firefox and your word processor (if necessary).
Word processor plugins for the standalone version of Zotero are also available from the "Cite" pane of Zotero preferences.
See the "Generating Bibliographies" tab for more information on how to use the word processor plugins.