Here is your diagram. That optional wire to the outlet is handy to charge the battery without having to remove the seat and tub. Use the leads that are removed from the outlet to power stuff like TPMS, GPS, etc. Terminals are all 1/4" and available at Oreilly's, Auto Zone, etc. They have the "piggy back" adapters you will need if you wire the outlet.
The fuse size minimum should be 10 amps for that 5 amp horn. Max fuse of 20 amps and the wire. Use 20 amps if you run a small compressor.
Make sure you got all the screws and nuts removed before you pull that nose off! (Voice of experience!)
Now WHY does this ROTATE the picture 90 degrees??!
Oops! Forgot the ground wire on the horn!