If you can't access your IP address, then it isn't because of your DNS. DNS stands for domain name system and translates domain names TO IP addresses. Thus, you must already have a reachable IP address for your A record to be meaningful. Make sure that you've configured your server correctly (Apache?) and that the necessary ports are open in your firewall (iptables).
Check that your domain registrar is pointing its name servers to the authoritative name server (the server with your zone file) for your domain.