DNS servers is how people find your website on the Internet. When you type
www.mydomain.com it goes to your domain register, then it goes to the DNS servers, then they tell the computer what IP the website is using.
www.zoneedit.com provides a free DNS service, is this a home webserver or is this a dedicated server? If its a dedicated server your provider should provide free DNS service.
Also are you wanting to set up your own DNS server on your webserver? I need more information if I am going to be able to help you.