Freezer Burn is based on a condition, freezer burn, that occurs when frozen food has been damaged by dehydration and oxidation, due to air reaching the food.
This is fairly easy. As long as you have Chilly Pepper unlocked, you can put it into your plant selection. Its only negative is that it wastes a seed slot, a Chilly Pepper, and sun. Because of this, it is best to waiting until you need Chilly Pepper to unlock this achievement.