To add a subdomain that points to an IP address somewhere else,
Go to manage domains in the panel. Don’t pick add a new domain or sub-domain, Instead click the DNS button underneath the domain in questions. Fill in the Section titled “Add a custom DNS record to DOMAINNAME.com”
Type A records are if you are going to point to an IP address, use CNAME if you want to point to a name that already exists in DNS, and “Value” is that IP address or name.
After you make your change, you may not see the change immediately. Remember DNS changes take time to propagate across the internet. Hint: if you have been playing with abc.mydomain.com and want to use/test your new entry more quickly don’t use abc.mydomain.com because it will already be cached and you have to wait for the cache to expire, instead use a new sub-domain such as xyz.mydomain.com that has not been cached previously and your entry will start working quicker.