How to replace gasket on freezer door?
This gasket should have a hard plastic strip along the back of it. That strip runs in between the door liner and the outer frame. Sometimes it is nessary to use a putty knife to assist in getting this between the liner and door. Make sure all corners and sides of the plastic strip are behind the liner of the door. Once installed it may be nessary to heat the seal with a hair dryer, being careful not to melt it, to form a good door seal at the cabinet. Your old one should pull off as this one goes on. Here is the part and a link to the parts diagram. Hope this helps.
Door parts replacement parts for WHIRLPOOL ET8CHMXKB04 REFRIGERATOR | AppliancePartsPros.com