Simply plugging your new router into 'Port 1' would appear to be a good start:
https://www.bt.com/help/broadband/whats-an-openreach-modem-ont
You shouldn't need to use the ADSL socket and, unless you're not going to be using a wifi connection to your computer, you shouldn't need to use the ethernet cable either.
All copper-cabled phone lines are being phased out, so it's possible that Openreach might have disconnected your traditional phone line when they installed the FTTP connection.