The lock cylinder and the bracket are notched. I am not sure the fender opening is notched, but I believe so. These notches dictate which way you should assemble the assy.
At the base of the lock cylinder there are two slots where the spring clip inserts (The horse shoe shaped clip) Make sure that is seated properly.
You will need to attach the cable before you slide the spring clip in too.
I am working off memory here, so I hope you hang in there with me.
1) Insert lock cylinder into the fender-align the notches.
2) Slide the bracket over the lock cylinder-. (Inside the fender)
3) Install the cable-align the notches on the bracket and lock cylinder.
4) Slide the sping clip in the slots at the base of the lock cylinder.
5) Place the end of the cable in the saddle at the top of the bracket, it should "snap" in place and stay. Its easy to bend, so be careful.
Make sure this works by turning the key in the lock paying attention to the movement of the latching mechanism under the tail. Do not put the seat or cover on until you are certain its going to work properly over and over.