I’ve flashed the OpenWRT image for the TP-Link WDR3600 from 2015-06-23 (http://snapon.lab.bufferbloat.net/~cero3/lupin/ar71xx/) and it has installed correctly.

How do I go about setting it up for my UK TalkTalk Fibre connection (using a VDSL modem connected to the TP-Link router: the TP-Link router gets an IP address via DHCP).

My sincere apologies if any of this is really obvious and I’ve been silly and missed it.