You can add a subdomain for an existing domain in the HSPC control panel with the following steps:

1. Click on the System tab.
2. In the Domain Management section click on Domains.
3. Click on the domain for which you wish to add a subdomain.
4. Click on the New Hostname button.
5. Type the subdomain portion of the hostname in the "Domain" text box.
6. If you have more than one IP address available, select an IP address from the drop-down box.
7. Click on the OK button.