Your Self-Book dashboard comes with 9 starter templates. If you want to modify these templates they can't be edited, but you can copy these templates and then edit the copy. Next to each of these templates (excluding the "Add Text Reminder" template), there is a "Copy" button that you can click on.
When you click on this button you'll be copying both the template and the Self-Book form that goes with the template. A pop-up dialog will appear where you can choose the name for your copied Self-Book template and form so that it's easy to find which form belongs to which template. See the image below:
After you click on the green "OK" button your Self-Book dashboard will automatically refresh and you will see your copied template in your dashboard in the "Customized 'Self-Book' Templates" section.