Hi there!

The template is using the default registration form comes with Joomla. So if you want a privacy policy checkbox in it then the following tutorial may help you:

https://www.gavick.com/documentation/joomla/terms-conditions-registration-checkbox

You may like to look into the following too I guess:

https://www.joomshaper.com/blog/introducing-brand-new-form-builder-addon-in-sp-page-builder-3-4-4-pro

https://www.joomshaper.com/blog/sp-page-builder-form-addons-which-one-is-best-for-you

Best Regards