Open and Close a div within a CMS item

Hello All
I have a project in process here:

…where I have a few ‘case study’ items from my CMS which I want to show/hide content pretty much exactly as I found here:

…I’m having trouble knowing exactly what to do, and even if I can mimic this great example? Any help would be great… thanks so much!


Here is my public share link: LINK
(how to access public share link)