If you are FTTB/FTTN, your router connects directly to the telephone wall socket, but the X1860 won't work here.
If you are FTTC, there is a white NBN box with 4 blue lights. The X1860 connects to this with ethernet cable. It needs to have first 3 lights on. 4th light is on when connected to router.
To configure the X1860:
Do factory reset.
Login to router admin on 192.168.0.1
On Settings menu, select Internet.
Select PPPoE, enter TPG username and password.
In Advanced Settings, select Dynamic IP.
On Settings menu, select Internet, then VLAN.
Enable Triple Play and Priority ID
For Internet VLAN: VLAN Tag - Enable, VLAN ID - 2, Priority ID - 0
IPTV VLAN and VOIP VLAN - Disable
Interface Traffic Type: LAN Port 1 to 4 - Internet