First you need to see your desired domain name available or not choose short, catchy and easy to remember domain name for your website. Use G-talk to search your domain name availability after adding email@example.com in G-talk friends list
A domain registrar is a company or organization who has been authorized by ICANN, the organization who oversees domain names, to offer domain registration services. A domain registrar normally has access to all TLD’s that are publicly available for registration. A domain name registrar is a service that allows you to officially register your desired website domain name so that it is unique to you, and no one else can own it. There are many domain registrar available online to register our domain.
Domain registration refers to the process of registering a domain name, which identifies one or more IP addresses with a name that is easier to remember and use in URLs to identify particular Web pages. The person or business that registers domain name is called the domain name registrant.
Goddy is the best reggistar for online domain.
A domain name registrar is an organization or commercial entity that manages the reservation of Internet domain names. A domain name registrar must be accredited by a generic top-level domain (gTLD) registry and/or a country code top-level domain (ccTLD) registry.