Howard,
You enter the dynamic DNS address as the SIP Contact in the control RRC. No further data is needed, all the control RRC needs
is to know where to find the radio RRC, which is this address.
If you have any further basic networking questions to set this up, drop me a short mail at dj0qn (at) darc.de and I will send
you my networking checklist to walk you through this process.
73,
Mitch DJ0QN / K7DX