Ah HA! Perfect.
That peice goes on above all the signal stuff.
See that little wheel in your column for the horn contact?
That copper surface on the back of the hub only goes down far enought to touch that wheel.
If you need it I can tell you the order the other parts that go on if you show a picture of them all.
Usually it would be,
That hub, the large cover, the big nut and 3 bolts, then the adapter can and wheel, then horn.
But this sometimes varies depending on the design of the wheel attaching bolts and horn button.
Don't forget you have to thread the horn wire from that hub up through the other things as you put them on.
On my new wheel from Forever Sharp the horn button hub bolts down with the same bolts that hold the wheel on.
On my old one (Grant) the horn button was attached to the wheel and the bolts that held the wheel itself on the adapter can were only to hold the wheel on the adapter can.
And if it seems like the hub won't go on far enough, make sure the steering shaft didn't slip down inside the column.
There is supposed to be a small ring that sits in a groove on the shaft to keep it up in place.