Remove the rear panel to access components inside your iPhone 4.
Power off your iPhone before beginning disassembly.
Your phone's rear cover may have two #000 Phillips screws or Apple's 5-Point "Pentalobe" screws. Check which screws you have, and ensure you also have the correct screwdriver in order to remove them.
Remove the two 3.6 mm Pentalobe or Phillips #000 screws next to the dock connector.
Push the rear panel toward the top edge of the iPhone.
Pinch the rear panel with your fingers, and lift it away from the iPhone. Alternatively, use a Small Suction Cup .