Teachers can make groups, for example to allow students to submit group assignments in Brightspace. You can join or view groups by clicking on Course Tools in the navbar of the course, and then on Groups.
Here, you can view whether you have been enrolled into a group automatically. If this is the case, you will see the groups you are in under My Groups. Else, the teacher may have opted for self-enrollment, then you can register yourself for a group in Brightspace.
Click on View Available Groups for an overview of the groups you can register for.
Select a group and click on Join Group. The group is now under My Groups.
If you have made a mistake and want to unsubscribe, click on Leave Group. Make sure you do this before the end date, otherwise it is no longer possible to register and deregister.