You can authorize in several ways:
A personal access token is a more preferable and flexible method of authorization, but if the team's server settings do not allow you to create one, you can use the password authentication option.
You can learn more about how to create your token in the official documentation: https://developers.mattermost.com/integrate/reference/personal-access-token/
For the initial configuration you need to specify the server URL (i.e. the workspace url of the Matermost instance) This can be extracted from the browser address bar by opening the messenger in your browser.
If you are a member of several teams at the same time, you must explicitly specify the default team name in the extension settings
You can choose to open deep links in browser or Mattermost application (default)