I don't know about the configuration of the ONU but I can help you with the
router setup.
In the router setup, first set the mode as Router, then in the connection select PPPoE as the connection type and in that you can enter the Username and password provided my Railwire. That should get the Internet to work.
If you face you can directly talk to the LCO to help you, I got mine setup by the LCO himself but I have reset the Router several times after that.