put this script line in your custom code section of the site, at the “before <body> tag”: <script type="text/javascript" async defer src="//assets.pinterest.com/js/pinit.js"></script>
Create a button on your cms item with this link: https://www.pinterest.com/pin/create/button/
Add custom <a> attributes to the link as following: data-pin-do="buttonPin" data-pin-tall="true" data-pin-round="true"
That’s it
I made a small example for a Pinterest save button here that you can look at and clone.