1. Create a user account for free with Eventable
  2. Build the button using the online wizard
  3. Input the event details such as title, start/end dates, description, location, or link
  4. Click Generate Button
  5. Choose your button style from the options
  6. Copy the code output within the Use the embed code on your website: field to the clipboard (Command + C on a Mac, Ctrl + C on a PC)
  7. Go back to your website you'd like to add the button to
  8. Edit/create a post
  9. Fill in a title and any other relevant data
  10. Make sure Advanced mode is enabled (the button in the lower right corner of the website)
  11. Paste code into the Display settings > Embed HTML field (Command + V on a Mac, Ctrl + V on a PC)
  12. Add the embed to the post's content field
  13. Save the post
  14. Admire the newly created Add to Calendar button :D
  15. Cheers!