How do I use this Custom Panel in wPF?

Question

Hi, I read this article: https://www.codeproject.com/Articles/32629/A-better-panel-for-data-binding-to-a-WrapPanel-in

 

It's about creating a custom panel. If you look at the bottom at the tiny section called "Using the Code" it's too brief for me to understand because I'm new to this. He makes it seem like it's a very simple thing to do I just don't understand what he means.

 

Could someone explain how to actually use the class he has provided please?

Thanks