If you want it to be available at anydomainonyourbox.com/php that’s easy too, though…
Lets say you installed it at /usr/share/phpMyAdmin. Whatever.
Now, log in to yourbox.com:10000 (webmin)
select "Servers – Apache Webserver – Default Server – Aliases and Redirects"
In the "Document directory aliases" section, add a matched pair with
"/php" on the left, and "/usr/share/phpMyAdmin" on the right.
Apply changes and restart apache.
now you can go to any domain on the box and get phpmyadmin, eg:
http://yourbox.com/php
or
http://www.virtualdomain.com/php
If that floats your boat.
Make sure you have the authentication mode set the way you intended in (sounds like you want http probably) in config.inc.php!
Good luck,
Tony