Make sure you have your curves layer mask (the one that controls the brightness of the photo) selected

Double click on the curves icon to open it for editing

Change it to make the surrounding area of the photo darker

Again make sure mask is selected

Select the round selection tool from the toolbar

Draw a selection around your subject, the area you want to be lighter

Hit control+backspace (also make sure your color palette is white on top of black as shown) This will make a cutout in your mask

To make the edges softer go to gaussian blur

Go all the way up to 250 and say ok

The following steps are optional. Its to give the greenery an extra kick. Its all pretty self explanitory, just make sure you follow up with the masking method shown before… we dont want the baby any darker now do we?