For .GR and .EU domain names you must log into your account at Papaki.gr, choose the domain you wish to get the Authorization code for, and click on the link "Send Authorzation Code",  in order to receive the code by emaill. For .com .net, .biz, .us, .org, .name or .info domain names you need to conact with your present registrar to get the authorization code. Many registrars let you obtain the authorization code through their control panel.