To start an engine, you will first need to make sure that the vehicle is in park (or neutral, if it is a manual transmission) and that the parking brake is engaged. Next, turn the key in the ignition or press the start button to activate the starter motor. If the engine is cold, you may need to press the accelerator pedal slightly to help it start. Once the engine starts, release the key or button and allow it to warm up before driving. If the engine does not start, check to make sure that the battery is charged and that all connections are secure. If the problem persists, you may need to consult a mechanic for further assistance.