help with 12 volt power supply

I have the two 12 GA wires already connected directly to the battery. It is the smaller 18 GA wire to the "switched" on sorce. I'll look at the back of the ignition switch and see what I can see there first than I'll look at the fuse box. The wiring was very easy but Its only me doing it so its a little difficult to keep turning the key and checking for power in the wire at the same time. Mostly just annoying.

Brian