With Simple Parallax you can make elements move with different speeds when you scroll. To activate it go to "Lay Options" and check "Activate Simple Parallax". In the Gridder you can now right click an element and set the "y-parallax" speed.
It is best to have the elements at the bottom of your page use a parallax value of "1", meaning they don't use parallax. Otherwise you might get a huge blank space at the bottom of your page.