The most common pathway to registration as an architect is to complete an Australian accredited qualification in architecture. A list of currently accredited qualifications is available here.
In addition to holding an accredited qualification you must also undertake relevant practical experience and successfully complete the Architectural Practice Examination (APE).
Upon successful completion of the APE you can apply for initial registration as an architect in NSW by completing Form 01 - Application for Initial Registration as an Architect in NSW.