Enter the make and model along with eh words "service manual"into a Google search and download a PDF copy. Don't bother with all the sites that want to sell you one - there will be an official manual and it will be free. Carefully follow the instructions. You'll also need some small screwdrivers, a magnet to catch screws before they disappear inside and an old credit card to ease the case apart without scratching it.
Post back when you have the manual if you have any doubts.