Click the team wall and then the link with the member count in the navigation. You will get to the list of team members and at the top you will see the Subgroups button.
After clicking the Subgroups button you can create subgroups and divide members into them as needed. For such subgroups you can then organize events separately within the team, or add posts to the team wall intended only for the given subgroup – members of the other subgroups will not see such a post even though they are part of the team as a whole.
Team managers can be assigned to subgroups in the same way as regular team members.
Team subgroups can be managed by anyone who:
Is part of the managers of the given team, or
has Management permission for the Teams (read and write) module. The access scope must be complete.