Car just clicks when I turn the key

That is the classic symptom of a loose or dirty battery cable. If you are hearing a rather loud, single clunk each time you turn the ignition switch to "crank". If you hear a real light click, that is some other relay turning on or off. Use a test light to measure the voltage on the large wire bolted to the starter. You should find 12 volts there. Now have a helper try to crank the engine while you're holding the test light. The voltage should drop a little but not go to 0 volts. If the test light goes out, there's a bad cable connection or the battery has a shorted cell.