Domain Name Question

[Seanna Jordan]

All,
When I first set up our Frontier Server, I set it up to be 

http://<servername:port#

So, subsequent sites off of the site are:

http://<servername:port#/<sitename>

I have been asked to make these sites available from VPN, which means making
the sites named something like:  http://<sitename>.<servername:port#>  

Is there an easy way to do this?  If not, where do I have to manually enter
all information?

I looked for information on the Help site and was obviously not using the
right terms in my search.

I appreciate everyone's help in advance.

Thanks.

Sean