The edits here are super simple! But that's perfect, anyone can do it!
Here's what I did.
Open up both pictures in pixlr.
Then copy the picture with the people and paste it right over the top of the plain background picture.
You have 2 layers now. Then on the top layer (the one with the people) select that tiny carrot: Toggle Layer Settings (see picture)
It will bring up the OPACITY bar. This is the fun part. Just use the slider to make the people appear ghost-like!
Every picture is different. Some I took the opacity to 60% some only 73%...
Then you want to look at the layers and make sure they line up as good as they can.
Not always super perfect, but it gives it a vintage double exposed kind of feel!
Then I Desaturated the images...
You can also do sepia tones or old photo effects.