Shut off the power to the microwave by unplugging it, or by turning off the appropriate breaker in your home's service panel (breaker box). Attempt to operate the microwave to confirm the correct circuit is off and the microwave has no power.
Remove the screw located on the left side of the light cover and then push on the right side of the cover to open it. Remove the light cover, if applicable; otherwise, open the cover as far as it will go. The light cover itself sits directly over the light bulb and will be located on the bottom of the microwave, either on the left side or centered in the rear of the unit, depending upon the model.
Gently pull or twist the bulb out of its socket, depending on the model.
Insert the new bulb into the socket, pushing it in gently or twisting it into place.
Reinstall and/or close the light cover and secure it with the screw.
Shut off the power to the microwave by unplugging it, or by turning off the appropriate breaker in your home's service panel (breaker box). Attempt to operate the microwave to confirm the correct circuit is off and the microwave has no power.
Remove the screws from the top grille of the microwave, above the microwave door. Remove the grille by sliding it to the left. This procedure is easier with the microwave door open.
The light cover is located in the center or on the left side of the compartment behind the grille, depending on the model. Remove the light cover screws, then lift off the light cover.
Remove the light socket by pinching the clips holding it in place.
Pull the light bulb straight out of the light socket, then insert the new light into the socket, gently pushing it in.
Replace the light socket, then replace the light cover and grille to complete the installation.