How do I get classified in Australia?

Who runs classification in Australia depends on the impairment type, according to Paralympics Australia:

• Physical impairment: National Sporting Organisations (NSOs) run classification. Contact your sport of interest using the details on the Para sport pages.
• Vision impairment: Paralympics Australia runs classification for all Para sports in Australia, and vision impairment requests have their own request page.
• Intellectual impairment: Sport Inclusion Australia runs classification.

The classification FAQs say to contact your national sporting organisation a few months before you need classification. Classification happens at competitions or on separate classification days.

Sources: https://www.paralympic.org.au/classification/ and https://www.paralympic.org.au/classification/classification-faqs/