DNS Name servers

I host 20 websites, & want to do DNS myself to resolve these domains to my static IP. I have installed djbdns, & am slowly figuring it out. My question is,
In order for me to do this, I am assuming I have to register ns1 & ns2.mydnsdomain.com with the root servers. How & where do I do this?

I believe most domain name registrars (the ones where you purchased your domain name) allow customers to "create a new nameserver". By doing that, they will automatically be registered with the root servers after a day or two. Then you go back and change the DNS info for your domain name, namely, point your domain name to the new nameservers. At least that how I did it and it seems to work.

I guess I am confused then....
So if I change my nameservers for mydomain.com to ns1.mydomain.com, how do the root servers or someones browser know the IP address of ns1.mydomain.com?

When you create a new nameserver (usually at your domain name registrar's website, using a web-based control panel), you will just have to make up a name for your nameserver such as "ns1.yourdomain.com", and then you have to give it an IP address. That's the address you are talking about (which is the WAN IP address of your machine or router). After creation, your new nameserver will be registered with the upper-level nameservers by your domain name registrar on your behalf. Then wait a 24-48 hours (in my case) and the changes will be propagated throughout all the other public nameservers. Your dns server is then "public".