Registering a domain takes about 10 minutes and is pretty painless.
To register a .com.au domain (e.g. 123Host.com.au) you need some business credentials such as an ABN so have it ready. If you are after a direct .au domain (e.g. 123Host.au) and don't have an ABN, you will need to provide some evidence that you are an Australian citizen.
Click the domains link in the top menu to get started.