Choose Zotero for Firefox if:
Zotero for Firefox runs as a plugin for the Firefox web browser, not as a separate program.
The same version of Zotero for Firefox works on any computer that runs Firefox; there are no separate Windows and Mac versions.
Go to the Zotero Download page.
Click the Zotero for Firefox link.
When you see the message "Firefox prevented this site from asking you to install software on your computer," click Allow.
Click Install Now, and Zotero will download and install. You can either restart Firefox now, or wait until you have installed the word processor toolbar (below).
Word processor plugins allow you to insert citations and bibliographies directly into your documents. Installing them is optional but highly recommended.
Go to the Word Processor Plugins page. Choose the most recent version of the plugins if you're installing Zotero for the first time.
Word for Windows users: