Navigate to Devices -> Controllers and click on +NEW.
You will see the following prompt:
After entering your Device key and clicking VERIFY your Controller will be added to Supracontrol Enterprise.
Note: In order to successfully add a Controller to Supracontrol Enterprise, the Controller must be allowed by the network to access the Supracontrol Service.
Supracontrol Controllers have unique keys and cannot be added to multiple client accounts (not to be confused with user accounts which are part of a client account).