You will need to locate the vehicles power distribution box and the trailer tow relay block attached to it. This is under the hood on the driver side. You will need to open the cover to access the fuses.
The information for where the fuse locations are will be in the owners manual of your vehicle or even if there is a legend on the fuse box cover you can use that. You will be looking for the trailer tow electric brake and trailer tow battery fuse locations. For the relays you will be looking for the trailer tow backup lamp relay and trailer tow battery charge relay locations.
The Trailer Tow Backup Lamp Relay is position #38 in the power distribution box. The Trailer Tow Charge is position # 39 in the power distribution box.