Choose on a new layer the Brush Tool (B) to picture the grass as it is shown on the next image.

 

 



Find in Internet now different three trees of all shapes and a young couple of lovers, just to cut out these photos with the Magic Eraser Tool (E).



Place the trees and the couple on our picture and apply for these elements the here presented Blending Options>Color Overlay.



We’ll get this result:



Try to represent on a new layer the stars, choosing the Pencil Tool (B).