Web vs mobile picture display

Site URL: https://cooperco.squarespace.com/

I want to use a different background image for mobile and web so that It can be sized correctly for both versions. How do I use two different pictures depending on what format the website i being viewed?

Hi,

For top banner?

You can add 2 sections with 2 images, then we will give the code to show 1 on desktop, show another on mobile

Or we can give code to resize desktop image to fit on mobile.