yes, you need a tourist visa to Beijing, Mainland China, you don't need a visa to Hong Kong. You can submit the below documents to Chinese Visa Application Service Center (CVASC)in Brisbane or CVASC in Sydney/Melbourne according to the consular districts to apply for China tourist visa:
1. A valid original passport
2. One recently taken passport-sized photograph
3. One completed Chinese Visa Application Form
4. a copy of E-ticket or travel itinerary.