Fog in Editor with gradient fog

I am trying to set fog in Editor, somehow there is no fog option.
Further there is zone component and has rgb color for fog. I see (red), when camera is in zone, but no gradient depth. Why do not scene has it own fog option, rather than zone.

Also how to attach zone to camera.

Also how is zone/fog performance in basic mobile? does zone work on mobile phone?

Editor should have its own forum!

Thanks, it worked!

I would still like to know if fog is heavy on mobile device, I think it uses more or less same shaders as fogless shaders.
Also, what is the right way to set zone?
It seems so small as compare to scene.
Should I attach it to camera and set override for full scene effect? or
Is zone to be added to scene without node and full size of scene.
Also is there any default zone, then how do I access it parameter in Editor?
Is zone to be added to scene without node and full size of scene.
What does zone texture and below settings mean?

thanks in advance.