Hi
Sorry about the lack of documentation, I never got it as planned.
Anyway I did make a faq about shortcodes. For example, a join button should look like this for an activity named “Book Club” in shortcode: [acts name="Book Club" data="join_button"]
When a user joins by clicking it, it should turn into a leave button.
If you are using the blocks editor for posts then should be a dedicated shortcode block you can add. In the older version of post editors it should work anywhere in the regular text editor.