Make a Curves adjustment layer for tree and reduce the brightness.
Use a Photo Filter to bring back the colors.
Layer panel arranged so far :
Open up the png leaves image and place them to main document. Arrange the leaves to scene as much you want but make sure that arrange them in a way that looks like they are falling from the tree.
After arranging leaves to scene, apply 2px of Gaussian Blur to each leaves layer.
Select all leaves layer and group them by pressing CTRL + G. Change the blending mode of the leaves group to Normal. Now make a Curves adjustment layer, inside the group, and reduce the brightness of all leaves layers.
On the layer mask of Curves, mask the effect on those area of the leaves in which you think that this area will be less illuminated by the lights. Don’t hide the effect on those leaves that are in right side of the scene.
Use the Color Balance adjustment layer and enhance the colors of all leaves.
It’s time for final adjustments. Create a Brightness/Contrast, on top of all layer, and increase the contrast and brightness of whole scene.
Use the Color Lookup adjustment to boost the contrast of whole scene. Use the Crisp winter lookup file.
Reduce the opacity to 42%. Results :
Finally, use the Curves adjustment layer and reduce the brightness of whole scene.
On the layer mask of Curves, mask the effect on the selected area.
Final Results :
Layer panel arranged :
Hope you enjoyed the tutorial and do let me know if need any help.