For us older non-techno types, the easiest place to put the switch is between either the ground lead on the battery and what it is grounded to, presumably the engine, or better, in between the positive lead and that fat-a**ed stud on the solenoid down on the battery. For the one that I personally installed way back when, I went with the positive lead and routed it into....................................................(Uh-uh, that would be giving up secrets, and the whole point of that switch is to hide it so no one can "borrow" your ride to reduce it to parts or wrap it around a convenient tree.)
Nick
Nick