Starting at the top of the door, work the new door gasket into the track. Work your way down both sides of the door and across the bottom. Check for loose spots and adjust the gasket as needed for a proper fit.
Spread a thin coat of petroleum jelly along the sealing surface of the door gasket to help the new gasket seal properly.
Close the door and check the fit. The door gasket should fit tightly against the cabinet and door with no gaps showing. Smooth out any creases that cause gaps. Push the door gasket further into the track to eliminate gaps.
Turn the refrigerator back on or restore power to the refrigerator.
Use the same procedure to replace the freezer door gasket.