Hi Sally! That LO was from years ago but it is still one of my favorites. I'm happy that you are inspired to try it out! Here's how I did it.
-I made two copies of my sepia-tone photo
-The first copy, I clipped (Alt Ctl-G or Ctl-G ) to the SNU_SSAlpha_PhotoCollage_B-CollageSingleLayer .png.
-The second copy, (which is below the clipped layer), I changed it's blending mode to linear light and reduced the opacity to make it fade into the background. You might have to experiment on the modes and opacity to suit your photo.
-Depending on your photo, you may also have to erase or extract any distracting background features so as to make it blend seamlessly into your background paper.
I hope that helps! Please show your work off in the gallery. I would love to see it!