You set your own rates on your profile, based on your qualifications, skills and experience. Rates may also vary according to the duties required and the location of the job. During the day expect to earn between $18/hr (few responsibilities) to over $25/hr (or more for experienced nannies).
Conduct a trial search of carers on the site to see a range of the 'going rates' in your suburb. Your hourly rate quoted online should be 'gross' - it should include your tax.