If you can log in and see the openWRT welcome page in the terminal, that is good, that is what you need. Go back to there.
After this simply follow the tutorial Matthias linked on GitHub from point 7
After this continue fixing your network file and then the installation of your PB.
After this simply follow the tutorial Matthias linked on GitHub from point 7
So in order to edit files first you have to run mount_root, which will grant you read/write access to files.
After this continue fixing your network file and then the installation of your PB.