Drag the forest 1 image into our main document using the Move Tool. Click the second icon at the bottom of the Layers panel to add a mask to this layer. Select a soft round brush with black color (soft black brush) to erase the bottom and reveal the steps.
Make a Curves adjustment layer to darken the forest a little.
Go back to the stairs and create a Curves adjustment layer above the Hue/Saturation adjustment one. On this layer mask, use a soft black brush with a lowered opacity (about 15-30%) to refine the lightness on the steps. You can see the results on the mask and on the picture.