HECS-HELP is the loan you're getting to pay your student contribution amount* and that starts getting paid off once ur income reaches a certain amount
if ur a CSP student then ur entitled to HECS-HELP. if you're a fee-paying student then ur entitled to FEE-HELP which works the same way, CSP places are subsidised by the govt so some of the cost of study is taken care of by the govt and you don't have to pay it back (the rest of it you obviously do, e.g. through HECS-HELP), fee-paying places are not subsidised and students have to pay the full cost of their study (can still apply for FEE-HELP)
*student contribution amount is the rest (and I think majority) of the cost of study that you need to pay, given some of it is govt subsidised (for CSP students only)
all you need to apply for HECS-HELP is a tax file number so apply asap if you haven't, the rest of ur enrolment should be easy