Go to the following link and install the app
From Admin > go to App then install Auspost Shopify App & follow the installation instruction
After installing, to access the app in shopify go to admin > App ( Apps & sales channels ) > AusPost Shipping Quote & Book.
After Open Auspost App configure your Mypost Account.
Then add General Settings like Name of the account, API Partner Token (Manual) & check status to enable it or connect Account & Log in to MyPost Business
You can add other Carriers Accounts like Startrack & EParcel. Then add General Settings for Startrack & EParcel like Name of the account, Account Number, API Key, API Password, Volumetric Calculation & status.
To access a tutorial showing how this is done please click Here