asterisk users - Mar 2005 - polycom 500 help!!

Hi,

I'm just setting up my first Asterisk box.  So far everything is working 
fine.  I have the digium card in and connected to a regular telco line.  
The Asterisk box answers the line and goes through the demo voicemail 
functions.  Sounds great!

I bought a Polylcom ip500 phone.  I can't seem to get it to
"register"
with the Asterisk box.  Can anybody give me some clues as to:
1) What settings I  need in the sip.conf file.
2) What settings I need in the Polycom phone.

Thanks a million!!

-N