Hi @amybeveridge1 . Have you downloaded the user manual? It is quite comprehensive.
P129 has WAN configuration.
You are using the ethernet wan connection, so you may have to disable the other two or remove them.
P142 has ethernet wan details. Settings are PPPoE, username + @tpg.com.au and password.
Initially, Firewall should be unticked. But try it both ways.
If you are on bundled NBN/VOIP plan, set 802.1p to 0 and 802.1q to 2. (This is the vlan id.)