It goes in the hot lead to the coil from the key. The ones I have seen are a ceramic affair with two spades (male) sticking out one side and the resistance element visible on the other (kinda looks like a small heating element coiled around a rod, but it shouldn't glow like a heating element). On this end of the planet the parts stores like to call them a ballast resistor, I'm sure there are other names, but maybe that will help, I hope.
