You will be using NBN-FTTN. This will required a VDSL modem.
Not all older ADSL modems are VDSL modems and if not vdsl, it wont work.
If it is a VDSL modem, you can enter your TPG UN/PW and makde sure asetting called VLAN is on VLAN 2.
When you use a VDSL modem, it should work.
You may check the setup guide that we've created for NBN-FTTN here.