Push the door flap toward one side of the ice maker until the small tab pops out of the hole. The door flap has two tabs at the top of the flap, one on each side. The tabs hold the door flap in place and allow it to open and close.
Pull the old door flap out from the freezer and inspect it to see if the tabs have broken off. If the tabs are still connected, you do not need to purchase a replacement door flap.
Slide one tab from the new door flap into the hole that you removed the previous door flap from.
Pop the other tab into place on the opposite side.
Test that the door flap is secure by lifting it up and lowering it down. The flap should raise and lower without popping out of place.