The end product that you're going for is what will determine your method.
Assuming you want sweet cider. And the question is do you want it carbonated or not?
If you want it sweet and carbed, two methods work. Backsweeten with a non fermentable, and then prime it with a fermentable to let the yeast carb it for.you. this method needs no interaction after mixing. Just bottle it and wait. Non fermentables are things like lactose, splenda, stevia. I used this method with my first cider and took second place with it in a competition. I used 2tsp of steviol glycosides from my lhbs for a five gallon batch and a can of frozen Apple juice concentrate for the fermentable sugar to carbonate.
If you want to use natural ingredients and no artificial sweeteners then you have a more involved task. You would add sweetener to your batch little by little and then taste periodically. Once it is.to.your desired sweetness, you would then add priming sugar (corn sugar, frozen concentrate, Brown sugar, table sugar) for enough to carbonate. Then bottle. Once carbonation is at your preferred level, you pasteurize the bottles and you're done.
If you go with route two, I highly recommend reading every post in pappers sticky in this forum.
If you are new to cider and want to finish your product for drinking with little involvement I would recommend going with option #1