FIrstly, this isn't a "Skyline" issue.
Registration issues apply to all vehicles (believe it or not)
You can't transfer registration between states.
You will need to supply the RTA (or whoever deals with registrations in NSW) with current roadworthy certificate, proof of ownership, and any other paperwork that they require.
The internet is a wonderful thing....
http://www.rta.nsw.gov.au/registration/index.html