You need to return to the depot on the Northern Perimeter Road. I don't know why Enterprise an "in terminal" location as they don't have any cars/depot at the terminals. Five minutes from the Enterprise depot on Northern Perimeter Road to T5 is a bit optimistic. Allow more time.
If you intend to refuel the vehicle, research your plan first. There is no fuel in the immediate vicinity of the depot. (To be totally pedantic, there's a Shell just a few yards away - as the crow flies - but because of security control fencing, it's about a three mile road journey).
Once you are in the immediate vicinity of the airport, look for the specific rental return signs. You do NOT want to follow signs to the terminals.