In Control, click on the Device you would like to delete
Click the red DELETE DEVICE button at the bottom of the page

Click YES, DELETE DEVICE

If the device is online at the time of unpairing, it will reboot, then display a pairing code. If desired, it can be paired again.
Device Move
If you are unpairing because the device needs to be in a different Tenant, you can instead use Device Move.
If the device is offline at the time of unpairing, it will continue to play cached content until it comes back online.
This action cannot be undone. If you delete a device in Control, it will also be deleted from Beam.