After adjusting the foreground and background to taste hold down shift and select both, left click and choose " edit in photoshop " both will open in photoshop.
Drag the foreground pic on top of the back ground pic then use the drop down tab to chose blending modes. Using blending modes and the opacity slider for the top layer will give lots of options and results.
If the blending technique does not work for you mask out the foreground interest revealing the background. Can be done in many many ways either with the quick selection tool, magic wand tool, channel selection, background eraser tool, normal eraser or a combination of all.