Unplug the microwave from the wall outlet.
Remove the mounting screws securing the light cover to the underside of the microwave.
Unscrew the light bulb, and then screw the new bulb into the light socket.
Place the light cover back in position; secure it using the screws that were removed.
Restore power to the microwave.
Unplug the microwave from the wall outlet, which is often located in the cabinet above the appliance.
Remove the two screws at the top of the front vent grille, and then tilt the vent toward you and lift it out.
Pull the flat charcoal filter toward you are remove it from the compartment.
Push in on the locking tab, securing the bulb holder, and then pull the bulb holder out of the compartment.
Remove the light bulb, and then screw the new bulb into the socket.
Re-insert the bulb holder, and then return the charcoal filter to the compartment.
Replace the vent grille, and use the screws that were removed to secure it into position.
Restore the microwave's power source.