Skie

You are not the registrar. At best you can be a reseller for a registrar. To be an officially credited registrar, you need to contact ICANN and gain credidation (I know I didn't spell that right) through them along with paying a fairly heafty yearly fee.

What you'll need to do when you login to your registrar is Create/Setup Name Servers. Each registrar will have a different process of doing this, but they should all have a FAQ on the steps needed. This is where you designate "ns1.yourdomain.com" to be your public IP address. However, I believe that 2 unique (and static) IP's are required for this, so you'll need to set up both an ns1.yourdomain.com as well as an ns2.yourdomain.com (1 IP per Name Server). These IP's are the ones to your DNS server that you've set up. That's all that's needed to be done at the domain registrar. Keep in mind that it may take some time for anything you do here to fully propagate over the internet (up to 24 hours, but usually less).

After you have that all set up, you just need to configure your own DNS server and ensure that your DNS zone is properly set up. Once it is, there's not much else that needs to be done. Your DNS server is now considered to be the authoritative DNS server for your domain and will be contacted whenever someone wants to visit your website.