Blackerninja

I have a Quickcar switch panel in my 1991 SR hatch, and the fuel pump is already wired to it.

I want to retain the security of having to have the key in the ignition to start it but be able to start it with the momentary switch on the panel.

How should I go about doing this? I'm not completely sure on how the ignition system works, but I'm blindly guessing that power is supplied to the key cylinder and when turned to acc, power is sent to the acc relay, switching it on, and then when it's turned to start, power is cut to acc and it sends power to the starter?

If that is completely wrong, forgive me for being ignorant, I've tried to research it on the forums and have looked through the diagrams in a chilton manual but don't want to go chopping away at wires because I've had wiring gremlins in the past and it sucked.