Anna, whatever image processing program you use it would be the same:
1. Open the multi-photo file
2. Draw a square marquee around one of the photos
3. Edit--copy
4. Open a new document of the same size as the copied pixels (Photoshop CS does this automatically, perhaps Elements does also)
5. Edit--paste
6. Optional step: rotate to correct orientation (necessary if you've put photos on the scanning bed in sideways position to save space)
7. Save this new file under an appropriate name.
8. Repeat for each of the photos in your multi-photo file.

After all this, you can edit each individual file as usual.