Cadillac wont start or turn over?

No car can start until it turns over. Meaning the starter has to engage. So you have at least one problem or more. You have to have a good battery and it has to be 12.6 volts and remain at 8-12 vol;ts while trying to crank. When you cut the ignition on - the instrument panel has to light up and when you go to "start " you have to hear a soleniod in the starter go clunk. No clunk? There is a problem in the circuit to the soleniod. Clunks - but no turn over? Bad connection from the starter to the battery or bad starter.