Turn off the power supply to your microwave by either turning off the power from the circuit breaker or unplugging the power cord.
Open the microwave door, and insert a flathead screwdriver along the side of the button plugs located on the top left and right hand sides of the microwave door.
Press down on the screwdriver to pry out the button plugs, then remove them from the door.
Remove the two screws that were under the button plugs using a Phillips screwdriver or a flathead screwdriver, depending on the type of screw used to hold the door together.
Remove the screws from the top mounting bracket with the appropriate screwdriver, holding the glass in. Lift up and remove the mounting bracket.
Slide out the outer door glass, and set it aside. Insert the new outer door glass part into the front of the door.
Place the mounting bracket back onto the top of the door, and reinsert the screw. Reinsert the two screws into the top of the door.
Press the two button plugs back into place, then close the microwave door. Turn the electric power back on.