Add a Domain Name and Retain the Original One

[Chris Rempillo]

I want to add a domain name and retain what I am currently using, pacificpolytech.helioho.st 
and add this one
pacificpolytech.dpdns.org

can I switch on to this newly (will be) added custom domain name if I want to then switch on to pacificpolytech.helioho.st domain
if I needed to? thank you

[Chris Rempillo]

Because I don't have an option to add a domain even Johnny server has up to 10 domains that can be added why is that so