If you have the rheostat type switch you run a hot wire from the switched side of the ignition switch to the heater switch and a wire from the output side of the heater switch to the hot wire coming from the heater blower. If the terminal use on the rheostat makes a difference they should be marked in some way. If there's no markings it probably makes no difference which you use. If you have a multimeter you can determine which is which fairly easily by checking the resistance through the switch as you turn it through it's normal travel then reversing your leads and doing it again.

Save a life, adopt a senior shelter pet.
The three main causes of blindness: Cataracts, Politics, Religion.
Name your dog Naked so you can walk Naked in the park.