1. There should be a hot wire coming from your amp meter to the "bat" terminal on your switch.
2. There should be a wire from you "ign" terminal on the switch to your + side of your coil.
3. There should be a wire from the "S" terminal on the switch going to the starter relay/solenoid "S" terminal.
If it's burning your wire as soon as you turn it to the "on" position you have a hot wire going straight to ground somewhere. what I've described is the most basic wiring on any early model gas engine. There may be more wires but this should keep you from burning your wires.