What version of Premiere Elements and on what computer operating system is it running?
You will need to stack the images on different tracks.
If there is no transparency in the images, then the image on the highest track will be the only one seen. Consequently, you will need to create this transparency so that the images below can be seen.
1. Scale the images on each track so that each does not occupy the full frame.
a. right click the monitor, select Select, and then click on the file name of the image that you are going to scale
use the bounding box handle of the selected image to scale the image down
b. highlight the clip to be scaled and use Applied Effects Tab/Applied Effects Palette/Motion Panel expanded's Scale for the scaling.
Select a suitable background for Video Track 1 and then use the Picture in Picture feature..See fx Effects/Presets/one of the static PiP effects.
Drag the PiP effect into the image on Video 2.
Drag the PiP effect into the image on Video 3.
and so on...using the mouse cursor to move the images into place and size them further if necessary.
Please review and consider. If any questions or need clarification, please do not hesitate to ask.