All domains registered are root or naked domains, e.g. mydomain.com. They cannot be registered with www at the beginning, like www.mydomain.com.
When setting up your domain with your Zenfolio account, you will add the necessary DNS records in your iwantmyname account first. The easiest way to do this is with our one-click setup, and then you will need to complete setup in your Zenfolio account.
Be sure to use www.<< domain.tld >>, which will enable visitors to access your site using either the the root domain or the www variant.
If you try adding the naked domain in Zenfolio, it will display a "naked domain" error. Adding "www" to the beginning of the domain will fix the issue.
Zenfolio instructions: Using your custom domain with iwantmyname.com