Yeah as this picture shows...
... Before you attach the steering wheel, slip the boss over the spline so that the back plate touches the spring connector (Make sure the horn button doesn't make contact with the boss as it may make you jump if it is wired up backwards

). Then once the boss is in position, literally tap the bare ended wire on the boss. Hopefully the horn
shouldn't sound.
If it doesn't sound, hold the bare ended wire in contact with the boss and whilst in contact, push the horn button. This should then
sound the horn. In which case, sweet, all you need do is sandwich that bare ended wire between the wheel and boss like what's already been said. (Although you obviously want the wheel to sit flush on the boss)
That should really be the only option you'll need with that style of horn as that will complete the circuit. If it doesn't, obviously report back
