How do you change the alternator on a 2009 Ford Fiesta?

To change the alternator on a 2009 Ford Fiesta, first disconnect the negative battery terminal to ensure safety. Remove the serpentine belt by releasing the tension from the belt tensioner, then unbolt the alternator from its mounting bracket. Disconnect the electrical connectors and remove the old alternator, then install the new one by reversing the process, ensuring all connections are secure and the belt is properly tensioned. Finally, reconnect the battery terminal and start the engine to test the new alternator.