Ideally you want the return directly from the pump. Which means just straight up from the pump, no elbow bends that would restrict and reduce flowrate. However this is most of the time not possible.
Many people place their return just next to the overflow. Thats for convinence. But as far as im concern, as long as the pump is strong enough, the water would be spread out all over the tank instead of just returning to the overflow and cycle again.
Positioning could be anyway depending on what flow type you desire. For a more evenly spread flow, I would suggest returning in on the extreme opposite end of the tank so that most of the water in the aquarium moves from the return to the overflow, back down the sump and to the return.