Create an account at Zotero.org. Whether you use Zotero in its original form or the Juris-M adaptation, you will need to start with a free account. Your account allows your Zotero/Juris-M collections to sync between the browser extension, the web library, and the desktop app. It also allows you to share material and collaborate with other users. While not necessary to use these tools, you may also use your account to upgrade the cloud storage associated with your Zotero account at fairly reasonable cost.
Download Juris-M desktop app: https://juris-m.github.io/release/. The app is available for both Mac and PC users. If you currently have the Zotero desktop installed, you can still install Juris-M. However, you can only run one of these two desktop apps at a time.
Download Juris-M browser extension: https://juris-m.github.io/release/. The browser extension for Juris-M works with Chrome and Firefox browsers on Mac and PC. It is not available for Safari.