Thanks for the replies.
This was much easier than I expected. I had already connected my iPhone previously using the USB tethering function so not sure if that made it easier.
Anyway I simply plugged in the new USB dongle and the router automatically connected. The only thing I had to do, mentioned above, was altering the IP address as there was a conflict between the dongle and the router. I opted to change the routers IP. After that it just works. It’s using tethering rather than the 3G/4G option but it’s working well.