I have a flight from YVR to EWR on United. I think I will be arriving at either Terminal B or C. I've looked at the map of EWR Terminal B, but it seems like the Airtrain is sectioned off? If I land in Terminal B, go down to the the Arrivals Level to pick up my baggage, will I be able to just easily go back up to the Concourse level to board the Airtrain? or do I have to check-in somewhere beforehand? Thanks!