There should be a purple wire with a white tracer that goes to the primer. That is your power wire. For ground there should already be a black wire coming out of the primer and grounded by one of the two mount screws.
OMC never used a toggle switch so that was wired after the fact. Regardless, one side of a momentary on/off switch should have a fused power wire going to it and the other wire should be the purple/white Easy enough.
