If you own domains elsewhere and would like them to be mapped to your existing hosting, so they resolve to the same website as your 'main' account, you need to make a 'Mapping' payment from your MyPANEL control panel.
You will find this in the 'GENERAL SETTINGS' section, '
Map Domains' Submenu:
Your domains will be seamlessly mapped to your current hosting, and administration of the domains, including E-mail for the domain, will be configured through your 'main, primary' domains MyPANEL.