8.) In the layers palette, click on the Sky layer, then click the new adjustment layer button (the half black/half white circle at the bottom of the layers palette) and add a Hue/Saturation adjustment layer. When the Hue/Saturation dialog box appears, just click OK for now, without changing any settings.
9.) Notice in the layers palette the new adjustment layer has a second thumbnail to the right of the Hue/Saturation thumbnail. This is the adjustment layer's mask.