Automatic numbering of headings

This can be done via CSS.

http://2ality.com/2012/01/numbering-headingshtml.html

To add CSS:

• If you are using WordPress 4.7 or later, use the “Additional CSS” option in the customizer.
• If your theme has a custom CSS option, use that to add the CSS shown above.

Learn to use the Chrome Developer Tools to help you see and test changes to your CSS.