There are a number of ski clubs and community groups that will support you in xc racing. Joining a group is a great way of making friends and racing as part of a club team. Many offer training groups which will guide you through the sport of racing both for juniors and adults. Check out DisocverXCski for more information on what clubs are based in Australia.
Clubs also run racing events that are held all over the Australian snow fields from the end of June through to mid-September, sometimes with 3-4 events on the same day across different resorts. Not all involve serious racing. Some may be purely social and others include lessons and some fun races at the end. The biggest club event in Australia is the Kangaroo Hoppet, which is in the Worldloppet series of international ski marathons. When you race you either put your club name down or school name on the race entry form.