Turn the freezer off, take all the food out, put pans of hot water in (to move things along), leave the door slightly ajar, and wait. The ice will melt and water will stream all over your floor - so you might want to have some dish towels laid out in front of the freezer. As tempting as it is, don't use anything to pick the ice off - you might break something. Personally, I have used a hair dryer to speed things up, but I don't know if that's a good recommendation.