If the engine does not start due to a discharged battery, you can use the battery of another car to start it, connected via jumper wires.
1. Place the cars close enough to each other to reach the jumper wires, but not so that the cars touch each other. If they touch, it can create an unwanted ground connection. You will not be able to start your car's engine, and a bad ground connection can cause damage to the electrical system.
2. Tighten the parking brake lever on both vehicles. On a vehicle with an automatic transmission, set the gear selector lever to the "P" (parking) position, and on a vehicle with a manual transmission, set it to the neutral position. Turn off the ignition.
3. Connect one end of one of the jumper wires to the positive "+" terminal of the discharged battery and the other end to the positive "+" terminal of the battery you are starting.
4. Connect one end of the other jumper cable to the negative "-" terminal of the starting battery and the other end to the engine block of the dead battery at a point as far away from its battery as possible.
(Information copied from the website mitsubishiman)