Getting your testamur authenticated is as easy as making an appointment with the Student Centre manager to have your original testamur and a copy signed. You can also get the Student Centre manager to authenticate your academic transcript. However, an apostille is a different process that does not involve the University.
An apostille is a document that has been legalised by DFAT for use in foreign countries that are signatories to the Hague Convention. DFAT will either affix or attach an Apostille Certificate or stamp onto your notarised testamur for authenticity.
Foreign governments or businesses usually require Australian notarised documents, as well as other Australian public documents, to be either "apostilled" by the Australian Government, or "legalised" by their Embassies or Consulates in Australia.
We suggest that if you are seeking this service you carefully read DFAT's website.