How to get internet working on installed freebsd 5.1

[Joe Dunsmore]

I installed freebsd 5.1 on my computer when it was not connected to any 
network (but my ethernet card was attached).  Now that my computer has a 
network connection, I can't access any internet sites, it says it can't find 
the host.  I've installed freebsd 5.1 on this same computer when it was 
connected to a network and the internet worked right away.  I also have linux 
on this computer and it can connect to the internet fine.

So my question is how do I get the internet working on freebsd?  Is there a 
simple command I can run or do I edit some text file?  Thanks.