The Fridge
Not to be confused with the football player
Step 1
Wait for the mountain to erupt at some point during the game. You cannot create this process, it happens on its own.
Step 2
Follow the path to the top of the mountain and go into the cave. Inside will be a blue glacier/rock thing. Grab it and head back to the mainland.
Step 3
Back on the mainland, talk to the man from whom you get the snowboard and oher stuff. He will ask you if you want to turn your storage bin into a fridge. Say yes, if you don't want these 3 steps to be a waste, and you will get a fridge.