If you have a voltmeter you will have to start at the battery and chase the circuit until you find a spot where you have lost power. Battery, starter relay, starter, firewall block steer column switch and so forth.
FUSEABLE LINK fry on you?
Do you have power inside the car with the key on? Defrost fan work?
Headlights on?
Bulkhead hot and melted at firewall?
I don't want to send you on a goose chase because it could be just a bad ground somewhere or a dozen other things.
Start the power chase first with a charged battery and find where your 12 volts are lost.
