To acquire a firearm you must be the holder of a current NSW firearms licence or permit. You're then able to apply for a permit to acquire a firearm (PTA).
The category of licence or permit you hold will indicate what category of firearm you're authorised to possess. For example, if you hold a category B licence or permit, you're only authorised to acquire a category B firearm.
As part of the online application you'll be asked to select a 'good reason' for acquiring a firearm. See Things to keep in mind for details.
You need to complete a separate online application for each firearm you wish to acquire.
A fee is attached to each application, however certain exemptions do apply.