If your site is already published to a subdomain and you would like to change it to a different one, you can do this easily:
- In the Sitebuilder, click Settings > Publishing.
- Click Unpublish Site.
- Type "Unpublish" to confirm this action, and click Unpublish Site.
- After your site has been unpublished, click Publish Site.
- Choose your new subdomain and click Next.
Your site will then be published to your new subdomain.