This video walks you through how to connect with classmates via online messages. It also show how to @mention and to call and video.

You can read more about how to Get started in your class team (microsoft.com) https://support.microsoft.com/en-us/topic/get-started-in-your-class-team-6b5fd708-35b9-4caf-b66e-d8f2468e4fd5?ui=en-us&rs=en-us&ad=us