If you have the papers for the goat, like when you bought it you got a registration application you should be able to call the registry and ask for instructions or what you need to do.
If it is a grade goat(no papers) it s possible to get it register as NOA which is native on appearance and then breed to registered goats until you get a few generations in then those off spring will be registerable. NOA requires someone else to look at your goat and agree it is NOA and then there is some paperwork stuff to do. Lookup the breed registry for your goat. If your goat is a mixed breed from registered purebreds and looks mixed you may be able to do the experimental registry. Lots of rules to these things.