05, you might need to be a little more specific about your setup. I have some PIAA offroads and they came with their own relay which included a fuse inside. I would suspect yours has the same thing. You should have a black box that has a rounded off side to it with a mounting tab on the other side. The top will come off which reveals a relay and a fuse. If you have this, then the main power needs to feed from the battery.
You can use a fuse tap for the POS for the switch side and I think PhilD has a great write-up for this (
http://www.h2southtexas.com/tech/12v.html)
Stomper and N2IT are right for normal situations but if your PIAA setup is new and anything like the ones I have, it is quite simple to install.
Give a few more details and I am sure we can help you out.