Asus RT-AC1200 setup for Snap!/2degrees fibre broadband

Hey guys, pulling my hair out here.

I've just got an Asus RT-AC1200 and am trying to get it set up for my Snap!/2degrees broadband.

Item: https://www.asus.com/Networking/RT-AC1200/

User Guide: https://static.bhphotovideo.com/lit_files/266681.pdf

I've spoken to 2degrees broadband technical support and they couldn't help me get connected. As with my personal experience, they couldn't find a setting for vlan anywhere. He's the instructions from their site: http://help.2degreesmobile.co.nz/app/answers/detail/a_id/196/~/what-settings-should-i-use-for-byo-modem%3F

Can anyone help me out here please? How and where can I find out what vlan tagging is and how to set it on my new router? :(