To authenticate an Autotask CRM element instance you must use the Username and Password that you use to log in to Autotask CRM.
You also must enter the zone variation of the base URL used to access Autotask as the Server URL. For example, if you access Autotask at a URL like https://ww2.autotask.net/Mvc/Framework/Navigation.mvc/Landing, then the Server URL is https://ww2.autotask.net.