You can change your username and replicated site, from your back office. Simply log in to your back office and select the "My support & Settings" from there you will want to select settings.
Once you have selected "settings" you will click on "referral site". this will populate the "website Address" widget. Click on the pencil to edit.
Now you can edit your website name and username.
Once you have put in the new desired website, you will need to mark the box below stating that you understand that both replicated site and username are being changed. Once you click the box the Save button will appear.