LOL! I didn't realize that wasn't your work PeeWee05:) Select the sky delete it and then replace it with a sky you like. Keep in mind that it still needs to be constant with the mood/weather of the image your changing. To select it, magic wand is a good place to start if your not familiar with any other techniques. If the green isn't changing you may be doing something wrong. Just read over it again and see if you followed the instruction.

I never intended to make art.