Greg, when I did this mod I used two stainless fender washers, one each between the light and the black Honda base. As I recall a hole has to be made in the center of the Honda base large enough to accept the bolt on the new light. Then, using a Dremel tool, I ground out the back of the Honda base in order to get the nut and a 17mm wrench in there to tighten the new light. You need to remove the headlight to do this.
When doing the wiring you will notice that there is only one hot wire to each light in spite of the fact that the lights also serve as running lights. You will only need a single element turn signal light to serve both purposes. The Honda computer does the rest. If you bought dual element lights, just ignore the running light wire.