How to get the arrow to scroll to the next section

This demo:

On the bottom there is a scroll arrow to scroll to the next section.
I found out there is a “content-section” wich has the option to show the arrow once a background image is used.
But how do I get the image to be scaled or stretched to the bottom of the screen, just like in the demo?
Or is there another content element wich I could use?

Thanks for the reply.