Place it lower than the basic layer of the sand. Change after that the layer's Blending Mode on Soft Light.



Merge down all the layers: Layer ? Merge Visible (shift+ctrl+e) and make a copy of the new obtained layer. Apply on this layer the next filter's option: Filter ? Render ? Lighting Effects.



Blur out the layer (Gaussian Blur).



After that, change the layer's type on Soft Light and minimize the Opacity till 40%.



Insert now on a new layer the picture of the sky:



Correct its sizes, selecting next option: Edit ? Free Transform (ctrl+t).



Make use of the selection shown here: Filter ? Blur ? Radial Blur.



Change the layer's type on Hard Light and increase the brightness of the layer (ctrl+m).