Freezing apples is a great way to extend their shelf life, and they can be used in many applications, such as applesauce, apple pie, or to add a bit of fiber to smoothies.
First, peel, core, and slice your apples. You want to keep them in slices to best preserve their shape and texture.
Then, soak the apples in enough cold water to cover, with a couple tablespoons of lemon juice. Let sit for an hour, and then drain on a wire rack lined with paper towels until any excess water is drained off.
Place the drained apples into a freezer bag laid flat, with minimal touching between the apples, otherwise they may stick in the freezer. Let freeze at least overnight. These will keep for 3-6 months, any longer and they may lose their flavor and the texture will start to deteriorate.