Unplug the Kenmore microwave from the electrical socket.
Turn the microwave over to allow access to its bottom, where the bulb cover is located. Use a screwdriver to remove the mounting screws from the bulb cover.
Open the bulb cover. Unscrew the burned-out lightbulb.
Put on gloves, then screw in the replacement bulb. Oil from your hands can cause the bulb to prematurely burn out.
Push the bulb cover into place and replace the mounting screws.