Very nice, Anita. (And I'm pretty sure you didn't align all those little squares by hand, did you?
I believe what you need is ctrl +G.
Irv here is a photo that gives you an example.
place your photo above the white square.
Make sure you are on the photo layer and it is highlighted.
Control +G will clip it to the black layer.
Now you can move it around or easily resize for what you want to show.
post modified thanks Kim.