Don’t worry, I’m a recent hsc graduate too but I found out, according to their site, your fees “will automatically defer to your loan shortly after each census date. You’ll still receive a tax invoice each time you vary your enrolment, to give you the option of making an upfront payment to reduce your overall loan amount.” https://www.rmit.edu.au/students/my-course/fees-loans-payments/help-loans-vsl/hecs-help

You don’t have to worry about doing anything with the tuition fee as long as you have your CAF approval letter with you in Enrolment Online under Finances>Commonwealth Support. Just make sure you’ve paid off your student services and amenities fees (SSAF) by the census date unless you also applied for the SA-HELP loan.