Scale the girl to fit on the bench. Here is where you add the shadows under her. I also duplicated the background layer and moved the top layer up a little bit so her feet actually fit on the layer.
step 7 of 8
Add a black layer on top. Select an ellipse from corner to corner. Feather it by about 100 px. Clear the center. Set the layer to overlay
step 8 of 8
Fixed the lighting (made her dress less bright on the light side and made the bench darker). Added some shadows under the bench. Made the girl a little smaller to fit the bench better.