chromebox stuck at user login ?

Hi all
i am trying to install LibraElec on a chromebox

I was able to get into DEV mode, i entered a couple of commands
o log in a DOS prompt (whatever it is in linux)
i was able to log in using SUDO something or other
but, then it asked me for a USER login
i can find no website mentioning this for help.

i can log back into chrome OS when i reboot
but, it will not recognise my USB stick.

it had mentioned i needed to enter a string to enable the USB fo boot options
but i cant enter the string, cos i cant log in, cos it asks for a USER login

thanks
Brad