The IP address is the IP address of your web server. If your web host gave you name servers to use, you will need to set your CNAME record with your web host, not us.
Although I register my domains at Dynadot, I use EveryDNS.net for my nameservers. It does support CNAME and many other features, so you may want to try it out.
Sorry, our Dynadot DNS options does not allow the setting of CNAME records right now. We are currently rewriting our DNS options to support more options, including CNAMEs. But it won't be ready for a few weeks.