Typical starter motor has a main +ve terminal for high current to the motor, and a smaller +ve wire from the key start to operate a solenoid (relay) which connects the high current +ve to the starter motor. Check that you have the smaller wire connected to the solenoid terminal. You can also jump from +ve on the battery to the solenoid and see if that makes the motor turn over. You are playing with high currents Here, and although it is only 12Volts, you can give yourself a nasty burn if you don't take care. Better if you can "phone a friend" if you are not into electrics on cars.