Polygon information is provided in several formats. The statistical regions of Australia are provided in levels 1 to 4 in the form of data cubes.
The following link can be used to download the Statistical Areas (Level 2) of Australia in 2016.
www.abs.gov.au/AUSSTATS/subscriber.nsf/log?openagent&1270055001_sa2_2016_aust_shape.zip&1270.0.55.001&Data%20Cubes&A09309ACB3FA50B8CA257FED0013D420&0&July%202016&12.07.2016&LatestUnzip the folder that has been downloaded, and note the extracted location.
Follow the steps in the read_shape() reference article to create a simple features data object.