The name server's A record needs to point to the IP address you have assigned to your site. You can check that by using any online DNS query tool. I just tried with dnsgoodies and the second box on the left showed the A record for a domain.
One other thing to note is that dns changes are not instant. You change it on your dns server, then it replicates across the Internet. Typically these changes take a few hours, but they will take 2-3 days in some places.