Here is the link to a youtube video that shows very simply how to add a Pinterest button to your blogger blog.
https://www.youtube.com/watch?v=MLJJI2XUcZoI had a bit of a hard time finding <body> as in my template it was not at the bottom, and there were several spread inside my HTML. So I tried out placing the code above each <body> until I found the right one.
Just be sure to save your HTML first, and use preview and be careful not to mess up the original HTML.
Here is the code:
<!-- Please call pinit.js only once per page --> <script data-pin-color='red' data-pin-height='28' data-pin-hover='true' src='//assets.pinterest.com/js/pinit.js' type='text/javascript'/>