How do I set *.domain.com

1) Create a wildcard DNS to resolve all subdomains:
User Level -> DNS Control -> add an A record:

* A 1.2.3.4

where 1.2.3.4 is your websites IP adresss.

2) Tell apace how to handle the wildcard:
#youre'r IP address
ServerName *.domain.com
ServerAlias *.domain.com
DocumentRoot /home/username/domains/domain.com/public_html