Confer domain name upon multisites

Dear kind board members,

I have installed WordPress 3.0 Thelonius, inspired by the prospects of having multiple sites for a single WordPress installation. I have indeed made a new site http://charles.chizeng.com/site2 off of my original installation on http://charles.chizeng.com/.

Now, I am wondering how I may confer a second level domain name such as domain.com upon my new site http://charles.chizeng.com/site2. Do I have to alter apache configuration files or DNS?

Thank you – any advice would be substantially appreciated.