For adding users to different groups.
Step-by-step guide
Click on the "Users and Groups drop down and select "Manage Groups".
Here you will see a list of all current groups. Select the "Actions" drop down next to the group you want to add users to. Select "View/Manage Membership".
Here you will see a list of group members. Click "Add User".
Click on the drop down and find the member you would like to add to the group then click "Add Member".
The user will now show up in the group and be effected by group theme changes.
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