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 latest Covid related official information for international travel to Australia is available at https://www.homeaffairs.gov.au/covid19
The travel requirements for travel to Australia by non citizens are continually changing. For example: from 21/04/2022 it is no longer necessary to have a pre departure negative test, but you must still provide proof of double vaccination and wear a mask while travelling on an international flight.
People planning to travel should check this website ( https://www.homeaffairs.gov.au/covid19 ) regularly to find the latest information.
There is a step by step guide to entering Australia by air at https://www.homeaffairs.gov.au/covid19/vaccinated-travellers/temporary-visa-holders/entering-transiting-australia/digital-passenger-declaration
Apart from being double vaccinated, the most important item is the Digital Passenger Declaration (DPD). You must complete and submit this in the seven days before you travel.
