When registering a domain, details are always recorded for the owning party of the domain.  This is referred to as the registrant.  If you pay for a domain, you are then the registrant - however it's very important to keep these contact details up to date in the interest of dispute resolution and the ability to transfer the domain.

By default, when you register a domain through us, we'll assign the details we have on file for you as the administrative contact information. If you wish to register a domain for someone else, or with different contact information, you can modify the under the Domain management section of your Client Area following your purchase. Alternatively, please contact support and we'll happily do this for you upon security verification. 

You can find out the contact information of the majority of domain names through any public "whois lookup", you can either use a web based search or a terminal command to view this.