The horn on my Chevy Joy isn't working

I already checked the fuses and connections; at the terminal that goes to the horn there is a + and a free one, at the steering wheel there is a + and a -, but I can't figure out how to make it work. In the lock box there is an indication that it has a relay, but it looks like it hasn't been connected.

First things first, find the horn and try to turn it on directly. If it doesn't work, replace it. If it does work, find the steering wheel, remove the front part, and turn it on manually. Close the circuit with the ground wire. If it's a ribbon cable, you'll have to buy one. It should have a relay, but it might be in a different place than where it says.