How to set up scroll to images without creating box?

I lost some files and am trying to recreate this page --> MF

If you scroll down a little there is a section where two images are laid over one another - one the of the images is scrolling while the other one isn't.

Forgot how to do it and tried using the scroll option for when filling in a box, but I'm sure I didn't do it that way...

Thanks in advance.