Like most countries, you will definitely need a visa to enter Australia unless you are an Australian Citizen or a New Zealand passport holder.The category of visa you wish to get solely relies on the purpose of your visit. If your country falls under the Electronic Tourist Visa (ETA), you can directly apply online and get it linked to your passport.
Otherwise the visa application has to be lodge early as possible keeping in mind that it might take time. Find Visa facility of the Department of Immigration and Border Protection website will navigate you to the application page where you can register for the Visa. The Australian Department of Immigration and Border Protection scrutinizes you before sanctioning the Visa.