I assume there are choices for this question? I'll just explain how you can increase possession utility in general and just relate it to possible ways on how to increase it in terms of a refrigerator.
Possession utility is the mere satisfaction you get from a good or service, it is, thus, it is subjective. However, ways on how to increase the possession utility for a fridge would be filling it with groceries, using it for your business (that makes use of a fridge), and storing food or drinks that need to be refrigerated.