I'm sure some things have changed on the Grand Cherokee since 1993 but....
I put a brake controller on my 1993 GC with the factory towing package. I also had the shop manual. The RV plug was already wired for a brake controller but the other end of the wire is left unconnected. I installed an electric brake controller under the dash just to the right of the steering column. I had to run a wire from the battery through a 20 amp (I think) circuit breaker, then through the firewall and to the controller. Another wire tied into the brake switch and then there was a wire coming from the controller that went to the wire from the RV plug. I think there was a forth wire that was tied to ground also.
I found the RV plug wire behind a little panel that is located by your left foot when it is on the foot rest on the drivers side of the jeep. Remove the panel and look for the wire. It was marked.
Caution: You need to protect the wiring from the battery to the controller. You can use a fuse, but if it blows you loose your brakes until it is replaced. I used a self reseting circuit breaker that you can pick up from an auto store. If it gets too hot, it breaks the circuit until it cools down. Then resets itself. So if you happen to overload the braking system and pop the breaker, it will reset in a few minutes.
Sorry so long but hope this helps.
2000 Jeep Grand Cherokee V8 Stock
93 YJ I6 hard top (really belongs to SPEED)
RE 4.5" Extreme Duty Lift, Advanced Adapters SYE, Tom Woods CV Drive Shaft, EA589 10" rims with 33" x 12.5" MT/Rs
Bullet Proof Front and Rear Bumpers and Tow bar