It's common for a site owner to start with a site address of http://dev.[domain] and, once the site is completed, update to a site address of http://[domain]. This is often called "going live" which means the development site that was private is now being made public.
When you want to change your site's address, enter a support ticket with a subject, "Update my site's address". Please provide the current address and the new address (it could be a domain or subdomain -- your choice). There are changes we need to make in the Wordpress install. It takes ~1 business day. Once the update is complete and we test the site is working at the new address, we'll send you a notice. Next, we recommend that you test the site too.
Also, make sure that you have pointed the new domain or subdomain at our server. If we find out you haven't done so yet, we'll contact you before updating your site.