Reading Microsoft's documentation, plus reading the README in my git repo of the Cordova plugin as the actions and interfaces are the same, plus studying the demo found here should get you up to speed.

You need to call the MsalInit action before you do anything else with the plugin. It tells the plugin how to function. You can call it without changing any of the input parameters, or you can modify them to suit your app. The options basically mimic Microsoft's published configuration and are documented in Service Studio's descriptions.