You will need a valid Australian Tourist Visa to enter Australia, unless you are an Australian citizen. The official government website is https://immi.homeaffairs.gov.au/visas/getting-a-visa/visa-finder/visit For most people the eVisitor visa (subclass 651) is the best. It is free, and you apply direct online.
The travel requirements for travel to Australia by non citizens are continually changing, therfore people planning to travel should check this website ( https://www.homeaffairs.gov.au/covid19 ) regularly to find the latest information.
People travelling to Australia will no longer have to complete a Digital Passenger Declaration (DPD) to declare their COVID-19 vaccination status.