How do you change the thermostat on a Ford Fiesta 1.25 16v fliar?

To change the thermostat on a Ford Fiesta 1.25 16v, first, ensure the engine is cool and disconnect the battery. Drain the cooling system and remove the hose connected to the thermostat housing. Unscrew the thermostat housing to access the thermostat, replace it with the new one, and reassemble the housing and hoses. Finally, refill the cooling system, reconnect the battery, and check for leaks.