So ...

Upon activation, go to Settings => Pinterest Pin It to access the plugin configuration page:

The first option will allow you to define where you want to show the "Pin it" button. You can select to show it on all pages, index or home page, single post, etc.

The second option will allow you to select the default image description that will be sent along with the pinned image. You can select from post title, post title and link, post title and site title, etc.

And that's all! The plugin will automatically display the "Pin it" button over your images according to your settings.

OK. Now let's see some closing thoughts ...