Go to zotero.org/download to download the latest version of Zotero or to install their browser connector.

Downloads are available for multiple operating systems, including Windows, macOS, and Linux. The Zotero download site will try to detect your operating system and offer the matching installer.

The Zotero Connector is also available for multiple browsers, including Chrome, Firefox, Safari, and Edge. The Zotero download site will try to detect your current browser and offer the appropriate connector.

There is no online technical support line for Zotero but this page will help guide you through some troubleshooting options: https://www.zotero.org/support/getting_help

Zotero also maintains an excellent "Documentation" tab to help you with a rich variety of tasks: https://www.zotero.org/support/