Rrrrrrr, need help on this one.

Un plug it anf throw in a new fuse. It has power to it at all times but it only passes current when you hit the horn button.
I don’t know how I can add a fuse when it has 4 prongs and I’m not going to hack up my horn relay harness. I’m in the process of buying another horn relay. At $20 a piece, I hope it doesn’t burn up too, lol !