If you want to register you own custom name servers and IPs such as ns1.yourdomain.com and ns2.yourdomain.com, (if you are on a vps platform this is required) below are the instructions.
1. Login to your GoDaddy Account
2. Next to Domains, click Launch.
3. Click the domain name you want to use to register as your own nameserver.
4. In the Host Summary section, click add.
5. In Host name, enter the host name you want to register.
NOTE: The value entered here will be appended to your domain name to create the host name. Do not use the 'www' prefix. Example: For the domain name coolexample.com, entering 'ns1' here results in ns1.coolexample.com.
6. In the Host IP fields, enter the two unique IP addresses you want to add to the host.
NOTE: Nameservers cannot share an IP address; therefore two unique IP addresses are required.
7. Click OK.