Pasturized cider you can just pour and pitch yeast. I just started a batch this weekend, but it's more of an apple mead. 5 gallons of cider, 6 lbs of honey and 6 lbs of brown sugar, with some "apple pie spices"
I'll tell you how it tastes next year!
but, it was store bought, pasturized cider, I heated up about 2 gallons to about 160-170 so that the heat would help dissolve the sugar and honey, then poured the last 3 into the carboy.
with unpasturized cider, I believe you add some type of acid treatment to kill any natural yeast/bacteria that may be in it, then pitch your brewing yeast.