vqadmin looks for a language folder based on the browser language setting.
So find out in the web server logs what the browser is requesting.
eg
en
en-us
en-au
...
Then create the appropriate language folder where vqadmin expects it and copy english over.
Translate if necessary.
Languages are in vqadmin/html, and are lower case.
My folder list looks like this:
-rw-r--r-- 1 vpopmail vchkpw 1625 Aug 11 2010 br
-rw-r--r-- 1 vpopmail vchkpw 1740 Aug 11 2010 de
-rw-r--r-- 1 vpopmail vchkpw 1492 Aug 11 2010 en
-rw-r--r-- 1 vpopmail vchkpw 1492 Aug 11 2010 en-us
-rw-r--r-- 1 vpopmail vchkpw 1736 Aug 11 2010 es
-rw-r--r-- 1 vpopmail vchkpw 1757 Aug 11 2010 fi
-rw-r--r-- 1 vpopmail vchkpw 1671 Aug 11 2010 fr
-rw-r--r-- 1 vpopmail vchkpw 1719 Aug 11 2010 hu
-rw-r--r-- 1 vpopmail vchkpw 1637 Aug 11 2010 it
-rw-r--r-- 1 vpopmail vchkpw 1544 Aug 11 2010 ja
-rw-r--r-- 1 vpopmail vchkpw 1634 Aug 11 2010 nl
-rw-r--r-- 1 vpopmail vchkpw 1496 Aug 11 2010 pl
-rw-r--r-- 1 vpopmail vchkpw 1483 Aug 20 2009 zh
-rw-r--r-- 1 vpopmail vchkpw 1483 Aug 20 2009 zh-cn
eg, if I wanted to add Australian support to vqadmin, i might do
cp -rp en en-au
and optionally change some of the spelling within that folder to Australian spelling standards.