1) You plug in your network cable, or set up the Wifi settings in the original dashboard... however, you can't play on Xbox Live (without breaking our rules here, if you ask for support on playing on Xbox Live with your RGH/JTAG we'll ignore your questions)
2) Enable "Beta Updates" in the settings, then just let it check for updates...
About the issue with not getting back to the original dashboard:
Hold RB to bypass the FSD Autoboot (hold RB while you are exiting to dashboard or booting your console)