Press the "Stop/Clear" button on the control panel of your Dacor Preference DMT2420 microwave to turn the appliance off if it is running.
Disconnect the power cord from the back of the microwave by unplugging it from the wall outlet.
Open the microwave door by pressing the door button on the front side of the microwave.
Remove the screws from the light cover on the right side within the oven using a screwdriver.
Turn the light bulb counterclockwise and lift it up to remove it from the microwave.
Insert a new light bulb into the light compartment, and turn it clockwise until it is fully tightened.
Place the light cover back over the bulb and reinsert the screws into the cover. Close the microwave door and plug the power supply back in.