It's simple just press the area where the camera is. The camera is loosened from mother board if you press the area around camera, then the camera will go back into the motherboard which will open your shutter. SIMPLE!! YOUTUBE shows..
http://www.youtube.com/watch?v=rFt0b-CfVrQ
Dear People,
I am sure that many of you have spent hard earned money on getting an iPhone 4. With that being said, I have put together some of the issues and possible fixes for the iPhone 4. If you come across any others, you are welcome to post them as well.

Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic