The ship docked at Barangaroo which is not as central as the overseas terminal. This wharf is also under construction and should be much improved when completed. It is not far from Darling Harbour or the Rocks and Circular Quay so it is possible to walk if you do not have any mobility issues.
There is minimal public transport at the wharf but a short ride in a cab can take you to the attractions. Sydney is a great city to visit and a ferry ride from Circular Quay is a way to view the bridge and opera house.