Heres a complete guide to wire up a kill switch so you can race at the track if your battery is relocated. Cut a length of electrical wire long enough to run from your switch to your ignition wires and connect one end of them to your switch.

Ke 3761 Motorcycle Kill Switch Wiring Diagram Schematic Wiring
How to wire a kill switch on a car. Sever the two ignition switch wires used to start your car. Crimp it tightly with the crimping tool. By using a wiring diagram for your car you should be able to find which wire is your ignition cable and determine the proper one to cut into. Step 2 choose a hiding place to mount your switch. Step 5 reattach battery terminal. Connect these wires to the wires you attached to your kill switch.
Make sure that when you install the switch that you install it in the on position. Do not use the 3 post kind as that is a lighted switch and easily found. With the terminal removed you can now install the kill switch. Also this can be used as a guide if you want to re. Once the wire is cut you can either solder the 2 ends of the wire into the switch or use additional connectors and crimp it on no soldering required. Connect the 14 wire that joins the power wire that goes into fusebox or ignition box to the connection on the toggle switch that is above the base of the toggle there will be only two connectors on the back of the switch.
Below is an ignition kill switch wiring diagram. Do the same for the other end of the wire that was cut. Wire the switch in between the cable and the battery terminal. You can also take it from the ignition coil or other fuses that can prevent the car from running. We install a kill switch to stop the fuel pump from running thereby stopping the car from starting. Chrisfix does an excellent job explaining how to locate the fuel pump relay and identify which wires to splice into.
Run two 14 gauge wires from the fuse wire that was just cut through the firewall to the ignition kill switch. Adding a switch between the cars computer and fuel pump relay ensures that even if theres power from the ignition whether from a key or hot wiring attempt the car will remain immobilized due to lack of fuel. Connect one of the wires to the length of wire coming out of the fuse with a blue butt connector. Connect the remaining 14 wire to the switch. Step 3 connect switch wires. Mount your switch inside your car where a car thief is least likely to find it.