I agree that the documentation would be easier to understand if it was formatted differently, but the GitHub link is a great top-down “how-to” of the plugin. Make sure you start at line 23, and read each & every line. All the explanation is in the comments and is broken into 4 steps; check for plugin dependency, register your shortcode, register shortcode UI for your shortcode, and then your stand WordPress shortcode function.
It’s worth noting that the dev.php file linked to on GitHub is an example of an additional plugin you can add to your theme to handle all of your Shortcode functions and the Shortcode UI. You could also take what they have available in that file and add it to your functions.php or a separate class in your theme.
