In addition to the permit for the Overland Track you will need a National Parks Pass.
For the months June to September no overland track permit is needed but you do need to register.
On the day you are booked to start the overland track you will register at the Cradle Mountain Visitor Centre. You will have to attend a compulsory briefing and then be provided with your actual permit that you attach to your rucksack.
You will also receive a bus ticket for the bus from Cradle Mountain Visitor Centre to Ronny Creek where the overland track starts and where you sign the visitor book.