I have changed my router, how do I pair the bridge to it please
You don't need to.
It should just work when you plug it in unless the router doesn't support 10Mbps half duplex connections on it's ethernet ports. Your ISP should be able to advise what if it will support that. If it doesn't, you will need to buy a small network switch to connect between the router and bridge. The switch will need to support 10Mbps half duplex
You don't pair the bridge to the router. If you already had a working Tado system, then you simply unplug the bridge from the old router and plug it into the new one. All three LEDs should light up to show the system is working.