van wheel and horn

[Peregrine]

When I bought my truck it already had a van wheel in it, but my horn doesn't work. This is starting to drive me nuts because the only way I can get someones attention at a light (if they don't notice it's green) is to pop it into neutral and rev er up. Not that thats bad, but people have been doing this a lot lately. I rmember one thread where you had to modify the plastic thingy from the van, btu I doubt I have that installed since the PO skimped on a lot of things. Pics of which one I need and how to do it would be helpful. I seem to remember a hard way and an easy way. Easy way involved soldering one wire somewhere. Anywho, all advice welcome and appreciated!