New to Photoshop. Stack layer question

Hello,

New to photoshop and been looking around to figure this out but no luck. I have two images stacked in photoshop. The top layer is set to lighten but its showing parts of the bottom layer (background). How can I paint parts of the top layer not to show the background layer? I tried taking a brush and changed the black and white on the left side but didnt work.

Thanks for your help!