If you want to register your domain name, you need to provide personal or company information as required by the registrar. You also need to provide Internet Service Providers (ISP) address or information about the host provider, and the names and IP addresses of two of their name servers.
If you don't have the name server information, most registrars can provide them and will automatically put them in the registration form. You need to provide all the details to registrar so that registration process gets faster and smoother.