Unplug the microwave power cord from the electrical outlet.
Open the appliance door to locate the light bulb cover panel.
Extract the small screw holding the panel inside the appliance, typically on one of the side walls, or insert a flat-blade screwdriver into the tab to pry open the panel.
Unscrew and remove the old bulb.
Insert the new bulb in the socket and twist clockwise by hand.
Replace the cover plate and secure with the screw or press the plate to snap the tab into the locked position.
Close the microwave door and plug in the power cord.