Horn is not working, need location of relay

I've a problem with horn not working at all. i checked the fuse 20 amp it was good. i would check the relay but don't know where it's located. some say under the hood fuse box, but i don't see it. no marking say's witch one is it black or light green and others say it's in the steering wheel on the lock spring. can you please tell me so that i can check it? Also, how to test it with a test light? they say it's a 4 pin relay but which one? please help in Dallas Texas.