Mist setting doesn't show up in scene/world properties. Help?

Support Compositing and Post Processing
1

–I’m not sure if this thread should go here, please move if required–

Hello, I’ve been trying to enable the mist setting so that my scene looks a lot neater, but somehow, it isn’t showing up, either in the scene settings or the world settings. My Blender version is 2.71, and I’m using cycles for rendering.

Screnshots:
http://i.imgur.com/OdkPvTSl.png
http://i.imgur.com/OoksbC3l.png

Cheers

2

Enable the Mist pass in the render passes then look in the World settings