After you look at the shortcode for a few seconds you should have a good understanding of what you need to do. Using the shortcode attributes of title, button_text, and button_link you can fill out the most important parts of the box.
In between the opening and closing tags of the shortcode you can freely type your own content just as you would any other post content. Use HTML tags and helper classes to style your content even further.
You can even leave the button fields blank and create your own button with HTML, that was just added in for your own convenience!
It’s also worth mentioning that you can also add the classes attribute to the shortcode to do even more with the box. For example, add these classes to any shortcode instance:
…and the width of the border box will responsively increase if you need more room inside your box.