If it is like a 99, just remove the plastic panel behind the spare tire on the drivers side in the back. In one of the cut-outs you will see connector plugs that connect the harness to the tail lights. Good luck.
go behind the spare tire, there is a panel that has to be removed. You will see some black connectors in there. You can by a wiring harrness that will plug into there without any cutting of the factory wiring harness. These work fantasic, as I have one in my 2001 Cherokee. this is very easy to do has the new harness plugs right into the vehicles. You can find this wiring harness at Walmart or any parts store it is made by Hoppe. Good luck and I hope I helped you. Semper Fi