how to apply HongKong visa at sydney?

Which country's passport do you have?
Many countries' citizen enjoy free entry to visit HK. If you are not qualified for that, you can prepare your valid passport, an application form, a recent taken photo, hotel bookings, round trip tickets, bank statement (if any) and travel plans to apply directly by mailing your documents to HK Immigration Department. In general, it takes around four weeks to get it in the end.