Making it appear as if someone is standing behind a wall

[steves]

I have a picture of someone I want to appear like they are standing behind a wall with their head popping over the wall. How do I do it?

Trying to rearrange layers but then the background of the image of the wall (i.e. the sky) just appears on top of it.

I know I'm missing something blatantly obvious, but any help would be much appreciated.

 

[Paul]

This will help you mate http://www.tutorial9.net/tutorials/photoshop-tutorials/working-with-layers-in-photoshop/