how ??

this is my domain >> www.world4sport.net

plzzzzzzzzzzzz help

You should be able to find a "transfer ownership" link on your registrar's site. Depends on the registrar, but I know that a couple that I use have this option.

Depends.

With some registrars you have to go through a formal procedure while with others you can go in and change all information including registrant.

Another option available if the current registrar procedure is too burdensome is to transfer to one that allows all information to be changed, then make the changes.

Just checked bulkregistrar.com which is where that name is registered. Here is their procedure.

Article Number: 40
Category: Making Modifications/Edits
Article: In order to edit the registrant field for a domain, please follow the
steps listed below.

1. Login to your BulkRegister account.
2. Click on "list domain"
3. Click on the domain you wish to
edit.
4. Click on "to edit a domain record use this form."
5. Click on the "edit" link all the way at the top of the page next to
the Domain Name information.
6. Input the new owner information
into the required fields.
7. Click "submit."

Please note that when selling a domain to a third party, it is highly recommended that you have a contract in place that explains the exact details of the transfer in ownership of the domain.