You transfer website from another server and want to check if website works ok before changing dns?
When you create website, there's a check box "Create Instant Alias" enabled by default to create domain alias for previewing website.
You can manually add subdomain of server hostname as domain alias to preview website:
1. Go to Domains, select Add Domains -> Domain Alias.
2. Add domain alias yourdomain.XYZ.premiumwebserver.com where XYZ.premiumwebserver.com is server hostname.
Please contat support if you don't know server hostname.