Simple Question on adding second domain

[M&J]

I have DNS running fine for my primary domain.  eg ns.somedomain.net
resolving www.somedomain.net.
I now want to add another domain to be resolved.  eg anotherdomain.com.
How do I add another one?  What do I need to modify?  Do I need another file
entry in the named.conf and then point it to another pz/anotherdomain.com?
Or would  I add it to the existing files?

Any help appreciated.  Is there a how to on adding another domain?

Mark