adding domain names to a vps

OPTION 1 :
Point your domain's A record to your servers IP address, this can only be done if your domain name provider allows you to set A records using the domain control panel.
OPTION 2 :
Signup for a free account at:
http://freedns.afraid.org/
Add your domains and sub domains to your afraid account, setting the A record for each domain to your servers IP address.
Then point your domain to the afraid,org name servers.

You may then create a VHOST in your VPS server using the webmin interface, please view the instructions below:
http://byet.org/createdomainwebmin.php
http://tutorials.securesignup.net/
http://tutorials.securesignup.net/vps-hosting/creating-new-sites-and-sub-domains-with-webmin.html

You need to restart your webserver after making any changes to your VHOSTS.

you may restart apache in webmin

or

SSH connect to your server and run:
/etc/init.d/apache2 restart