Frank, I am very surprised your horn wire broke because, well, it never moves. It is totally surrounded by steel and it is part of a bundle of many other wires. I suppose anything can happen.
All the wires exit your column just below your knees, when sitting. The horn wire is Blue-Yellow meaning, a blue wire with a yellow trace OR blue wire with yellow bullet connector.
Our wiring diagrams show seven wires exiting the column but really there are eight because the 'shift indicator lamp' (Red-Blue) wire isn't shown.
If you ground the horn wire, the horn will sound. This wire passes very low current, just enough to energize the horn relay coil. If you find the horn stays on all the time, a common fault happens when the horn ring is shorting to ground, from being assembled improperly.
A different fault happens when the horn never turns on. This is usually caused because the steering column has slid down too far and the carbon brush can not make contact with the horn ring assembly.
I like the idea of fixing your original wire if the break is in a convenient place. - Dave