Since it's kinda late, and I recently redid my steering wheel also. (You must also get Sport Z Magazine)
First note that there are 2 round pieces which are very similar to each other. As you compare both pieces, arrange them so that all their holes match up. You'll note that they essentially have the same holes punched in them, except that one piece has larger diameter holes,
The difference is so that the one with the smaller holes will be held above the one with the larger holes by the spring. This small hole piece will be mounted to the plastic with 3 screws and insulating washers. The Spring will push against the plastic to keep this plate separated from the lower piece.
The wire coming from the back contact plate, through the steering wheel will go through the plastic piece and the larger hole piece, through a large hole in the small hole piece, and then will be screwed down to the small hole piece. One of the holes on the large hole piece is there to allow the screw NOT to make contact.
The plastic piece has 3 posts, these fit through the metal piece with the larger holes and then the other metal piece fits on top.
The spring pushes on the plastic piece. When you push on the horn pad, it makes both those plates make contact and complete the circuit to ground.
I know this sounds really convoluted, but look at the pieces carefully, and you'll make sense of it.
One point to remember, when you replace the steering wheel on the column, make sure your wheels are straight, and most importantly, that the brass contact spring arm, is bent up enough to make contact with the contact plate on the back side of the steering wheel.
Hope this helped, I know reading it might not make a lot of sense, but if you look at the parts it will.
If it still doesn't make sense, either mail me or post, and I'll see if I can draw a diagram.