Horn wiring Ford Cab 12 8cwt

[david moore]

Having located where the horn should go from my other thread I now need some help on the wiring. The wiring diagram is not much help.
The horn has just one terminal (unlike my jeep which has two). There is the stub of one wire poking out from the base of the steering column. I believe the horn gets power from the starter solenoid battery connection but what's the rest of the story?