We may as well start with disassemling the bike
Open rear tool storage and remove the bolt that holds the rear seat assembly (10mm bolt) Remove seat and set aside.
Proceed next to remove the bracket that holds the front of the rear seat (2 10mm bolts) Lift the front seat and carefully remove the 2 wiring harnesses attached to it. Set seat aside.Remove the 2 bolts (10mm) that house the bracket for the front seat and also hold the gas tank in place. Set aside
Slide gas tank out of it's bracket and carefully place it so it doesn't fall. Some, at this stage might, want to completely remove the gas tank. Turn the valve on the bottom of the tank to off if you do this step. Using pliers grip the clamps holding the gas lines to the tank. When the clamps are moved you should be able to remove the hoses.
Remove the bracket that the top of the gas tank slides into. It's attached with 4 Phillips screws. If they have never been removed it's a good bet you will strip the heads. Before that happens I suggest using a small pair of vicegrips to get them started
Disconnect the stock horn which is located on the right hand side of the bike. After the wires are disconnected, determine the ground wire, note which one it is then, it's a good idea to heatshrink the exposed positive wire to prevent a short later

Next we need a source of power, which we can access under the left side cover in the fuse block. The top fuse protects the circuit terminals that are used to attach accessories. I'll suggest you replace the 10amp fuse with a 20 amp fuse while you are at it. Before replacing the fuse box cover when we are done I'll mention you'll need to open the top part of the cover so the wires will fit. I used one of the tapered sharpening stones that attach to my dremel tool.

***Note***
All crimp connections should be either heat shrunk or covered with electrical tape to protect against moisture. I won't repeat this through the write-up so don't forget it!!!

I'll mention that the relay will sit just above & behind the bracket that holds the gas tank. Check the above pictures to see where I mean.

Now that we have access to a power source, I suggest running a wire from the relay to here. DO NOT Attach to PowerYet!! The end that will attach to the fuse box is the U-Type mentioned in the what you need list, while the other end receives a Female crimp & can be attached to the relay. Route the wire down the middle of the bike and down to the fuse box, being careful that the wire will not be pinched & thus create a short.

Run a wire from the NEGATIVE horn wire (disconnected from horn) to the ground connection on the relay, again taking care that wires will be positioned to prevent pinching otherwise, you will Short the Circuit.

You now have two open terminals on the relay.
We now have to make a small wire with one end containing a female blade crimp 5 inches should do Put this aside.
From the compressor which is attached to the Suzuki Engine Guard ( Now Uner the Triple Tree Behind a Tool Pouch ) crimp a female blade crimp and attach to the positive terminal. Now run this wire up to the relay again being careful to postion it so it doesn't get pinched by the tank. I used enough wire to loop it towards the bottom of the tank mount and routed the wires up the middle channel.
Next I want you to join the open end of this wire with the open end of the short wire we made previously and crimp them together. The two terminals now available now attach to the open terminals on the relay. Next step is to attach the ground from the compressor. Test the horn button to see if horn works. Horn will sound without key in the on position.
If you prefer to have "Switched Power" Discard the directions concerning the 5 inch wire and run a "switched hot" wire to the relay in it's place.
I'll suggest that you wire tie all the wires running down the middle channel of the bike under the tank to keep them as positioned.
Re-install the tank holder, again being careful not to pinch the wires running under it and position the relay so it's not pinched by the steering head pivot!! Reassemble bike as you took it off.
If you wish to cover the wires with the black tubing now is the time to do sections you won't be able to access once the bike is re-assembled.
A tip in getting the tank smoothly back into it's holder, spray the rubber part with WD-40 and it will slide in without a struggle.