From your myCP page, Domains (in the left side bar menu) -> Domain List. The following page will contain a list of the domains you have registered with Superb, and clicking on the relevant domain name will provide you with links and information necessary to perform most tasks.
For customers with certain account types, or making certain more unusual changes, a support ticket may be required. Please note that support credits may be charged for any support tickets that involve actual changes or work performed.