It's really easy.
If you're using apples, you cut them up and cook them in a pot (I usually leave the skins on). I also squirt a bit of lemon juice in with them. (Seasonings are optional depending on what you might add in: cinnamon, nutmeg, etc) I usually use apples as a base and then mix in other fruits: pears, strawberry, kiwi, etc. (If you were just doing berries or something, you don't have to cook them.) Then you just puree it in a blender or food processor until it's smooth (you can add a bit of water if needed).
I line cookie sheets with plastic wrap and then spread the fruit in a thin layer over all the sheet. I let mine dry in front of a coal/woodstove with the air blowing on them, but there are recipies to dry them in the oven on very low heat. They do take a long time to dry, but when they're dry I loosen them from the wrap (so they'll be easier to peel later), cut them, and roll them up. (You have to make sure they're completely dry. They'll be flexible, like a thicker fruit roll up, but can't have wet spots.)
They will keep for a long time at room temperature, but I usually put them in a big ziplock bag in the fridge. I just made a bunch a put the extra in the freezer.
