View the groups available in your course. Each group shows the name of the group and how many members are part of that group.
If there are any self sign-up groups available to join, you can join the group by clicking the join link [1] or you can change groups by clicking the switch to link [2].
If you are already part of a self sign-up group, you can leave the group by clicking the leave link [3].
Note: You cannot leave groups that are not self sign-up groups.