It's on the top of the scene view. Also, make sure that the camera isn't set to ortho. Also, also, this is really a post for unity help. Not discussion. EDIT: Oh, and welcome to the forums!
You need to change the camera from orthographic to perspective. Unless you mean the editor, in which case there is a little 2D button at the top of the tab
This video will help you distinguish the difference. http://unity3d.com/learn/tutorials/modules/beginner/2d/2d-mode