Parallax is an easy feature to use that substantially elevates the design quality of your website.  

It gives your website the illusion of depth as your visitors scroll through your site, by combining multiple backgrounds that move at different speeds. 

To create a background with the parallax effect, fist make sure that you're in "Pro" mode. 

Add the background image you want to use.

Now, click on the container in which you want the parallax effect to show, and select "Edit." 

The following window will appear:

Here, simply check the "Parallax" option, and hit "Apply" to finish!