Need help with Collapsing Div's on Landing Page

Could someone give a me a detailed “show how” (I have almost no html experience) on how to use Collapsing Divs for my landing page.

This is the code I have found but tried a bunch of ways to implement but it doesn’t seem to function properly.

Div text

.divVisible {display:block;}
.divHidden {display:none;}

Thanks!