Need help wiring my horn

[turnjare]

Hi everyone,

I'm ready to hook up my horn on my 1949 3/4 ton. The truck was originally wired for a horn that was not grounded. The horn I have only has one wire coming out of it and I was told by a member of the forum that I needed to use a relay. I guess I'm not smart enough to figure it out on my own, so here's my question. I've attached a picture of the relay I want to use, as well as a diagram of what wires I have to work with. Which wire attaches to which post?

Thanks a million,

Jared