To use Zotero, you'll need to download two items:
1. The Zotero application
2. A Zotero Connector that will allow you to save citations to Zotero from your browser
This video from the Georgia State University Library demonstrates how to download and install the Zotero application.
Note that the Zotero word processor plugins are bundled with Zotero and should be installed automatically for each supported word processor (Word for Windows, Word for Mac, LibreOffice) on your computer when you first start Zotero. (Install a Zotero Connector for Google Docs integration.)
A Zotero Connector is the tool that allows your browser to communicate with the Zotero application. Using a connector, you can save citations to Zotero directly from your browser.
There are Zotero Connectors for the Chrome, Firefox, Safari, and Edge web browsers.
The Zotero downloads page will automatically detect which browser you're using and give you the correct connector link.
Just follow the prompts to download and install a connector. To troubleshoot, you can use Zotero's installation page.