Had a look at mine today. There are three holes in each side of the tow bar. Two per side to the frame, one to each bumper bracket. If you look at your bumper brackets, you should have a little bracket bracing between the bumper bracket and the frame. Remove those little brackets. The captive-ish stud coming down from the frame (retained by a big flat head welded on so it won't spin) goes through the rearmost frame mounting hole on the tow bar*, and the hole in the bumper bracket should line up to the hole on the side of the tow bar (hopefully you saved those fasteners off the donor). BF-8 of the '95 FSM shows how it goes together without the hitch if you want a better idea of what it is you're removing.
If you lift the hitch up and get the rear holes lined up, you should be able to see if the front holes are present and correct. I'm not sure if there's supposed to be a nut welded inside the frame or a plate or what. Hopefully they're where they're supposed to be and the threads are clean enough to use.
*I don't know if the tow bar kit came with alternative hardware for this stud, or if you were supposed to reuse the stud that held that little bracket on. If you got the hardware off the donor, I'd compare and use whatever looks stronger.