For what your asking, you won't be able to. All domain names and TLDs are controlled by the ICANN at the highest level.
http://www.icann.org/new.html
Then, things filter down from that. There's the master dns servers in the world, which are accessed by the registrars, and you register for a domain name at the registrars.
If you wanted to start your own .tk service, you'd have to start a petition I think, and then begin the request process with icann, but this is where my knowledge of those details gets hazy. It's a long difficult process, and usually costs a couple thousand dollars to go through, but it's the only way to get your own TLD that is recognized by the rest of the world.
There is also the name.space project which is petitioning the government to allow for some privatized TLDs, but I don't think it has happened yet, but you can work on helping them if you wish. Url is
http://namespace.org
That's about all I know with TLDs and getting ur own.