newbie DNS/BIND question

You haven't mentioned what exactly you're doing. Is this DNS server for serving Virtualmin hosted domains?

If so, you don't have to do much. Just make sure the NS server in the Module Configuration matches the one you created at your registrar. And, assuming you have a secondary server, if you follow this guide it will automatically be included in the zones of your virtual servers:

http://www.virtualmin.com/documentation/id,dns_slave_auto-configuration_...

So, in short, you don't need to do anything in the BIND modules, usually, if you're using Virtualmin, as it will create the necessary NS records. If you only have one DNS server (perhaps with two IPs), you'll need to explicitly add an extra NS record to the Server Template(s) that you use in the "BIND DNS Domain" section in the field labeled "BIND DNS records for new domains" . Just leave the option labeled "Add above to automatically generated records" checked, and you only need provide a single NS record like this:

${DOM} IN NS ns1.example.com

I'm not sure if I'm really getting at the heart of what you're misunderstanding...so I'll also point out the BIND docs for Webmin, which give a pretty good overview of the DNS system and might give you some hints on how to proceed (or what questions you need to ask to get better answers from me):

http://doxfer.com/Webmin/BINDDNSServer

And you might find some of the bits of the tutorials about BIND useful:

http://doxfer.com/Webmin/Tutorials