Hello,
Unfortunately, there is no video available for the Single Product Builder. However, it is not difficult to use; simply give it a try as it is similar to the Header Builder, but with sections.
If you would like, we can create an example for you.
To provide wp-admin access, create a new user account with administrator role via the Dashboard, and provide us with the username and password via the Private Content area.
Kind Regards,
8theme team