IPhone has two major casing part which must be removed to open your I-phone. One is the small black case which can be found on the back-bottom side of your iphone. This part of your iphone is fixed without any use of screws, so you don’t need a screw driver to open it. And the second part of your iphone which is the major silver back of your iphone. This silver back is usually fixed with small screws, so you mush have a small screw driver kitt to isolate that part. Now you need to follow exactly the following given steps in order to open your iphone.
Put your iphone on a smooth place like cotton bed or a 4 fold (at least) cloth. Make sure that you are seeing the black and silver part in fornt of you.
Now use a cutter or the knife kind of thing, which must not be very sharp, to simply drive out the black part towards downside of your ipone. In this way you can see a small gap between the black and silver part. Just apply some force towards downside of the iphone and the black part can easily be removed.
Now when the black part is successfully removed, you can see some screws under the black part. Now use screw driver to open the screws one by one. Remember do not apply large force, this can damage the sides of the screws.
Now when both the screws are opened, use the cutter again to pull out one by one the both sides of the silver casing. This step can esily be understood through the video. Anyway when you dive out the silver casing you need to push it harder because it was fixed so tightly that a small force would not be helpfull. Now when both the sides of the silver case are pulled out, you need to apply a force towards upwart to drive up the silver case.
For complete understading the abover process kindly see the video as well.