Have you seen our SOP: Handling sealed radioactive sources?
This contains the relevant information and is based upon the https://www.arpansa.gov.au/regulation-and-licensing/regulatory-publications/radiation-protection-series/guides-and-recommendations/rps18 We recommend downloading and printing this guide from ARPANSA.
The need for registration depends upon what sources you have, and the requirements set by the radiation regulatory authority in your state/territory. Links can be found on the ARPANSA website: https://www.arpansa.gov.au/regulation-and-licensing/regulation/state-territory-regulators
Follow the link for the regulator in your state/territory and follow the information on their website or contact them directly if you need further information.