From the Control->End-Systems Tab, highlight a user and either click Add to Group or right Click and Add to Group
You can then Select from Pre-Defined groups. see link in Additional Notes
Then add a description to the device, then Click OK
You will need to verify its removal. Click Yes and understand that unless the device is re-authenticated, it may not change it's current state and role.
If you now select from Control->Access Control Tab->Group Editor->End Systems Group, you can then select your specified group to see the added device.
The below screenshow shows the added device in the group.