Step 1: Go to Menu, then “Sip Trunks”, and "CT Cloud SIP (Meta)"
Step 2: Select your trunk
Step 3: Click on Sip DIDs, click on the DID to expand, enter in the forwarding number in the 'Unconditional enabled' field (for a permanent forward) or in the ‘Unavailable enabled’ field (for a forward if the number is not reachable). To save, you’ll hover over the pink circle with three lines and then click the “Save” icon