How do you can start a Cessna 172 engine with external power?

To start a Cessna 172 engine with external power, first ensure the aircraft is in a safe position and the master switch is off. Connect the external power supply's positive lead to the aircraft's battery positive terminal and the negative lead to a suitable ground point on the airframe. Turn on the external power supply, then switch on the master switch and attempt to start the engine as usual. Once the engine is running, disconnect the external power supply in the reverse order of connection.