Car horn fixes?

my uncle gave me his car for $600 only thing i have to fix is the horn. I have no idea how to do that and i don't have much money to get someone to do it for me can anyone tell me what i can do i need to get this fixed for it to p inspection and stuff if someone can give me instructions to install it myself i could probably figure it out but i just need some information before i start digging into it blind. the car is a dodge plymouth breeze if that makes any difference but i could really use the help