Here's how to jump start a car with a broken alternator:
1. Park the working car close to the car that needs to be jump-started.
2. Turn off the engines of both cars.
3. Connect one end of the jumper cables to the positive terminal (marked with a "+") on the dead car's battery.
4. Connect the other end of the positive jumper cable to the positive terminal on the working car's battery.
5. Connect one end of the negative jumper cable to the negative terminal (marked with a "-") on the working car's battery.
6. Connect the other end of the negative jumper cable to an unpainted metal surface on the dead car's engine block.
7. Start the working car and let it run for a few minutes.
8. Try to start the dead car. If it starts, let it run for a few minutes before disconnecting the jumper cables.
9. Disconnect the jumper cables in the reverse order that you connected them.