far side away from the red steam engine.

King's Cross railway station's train entrance faces north, and it's passenger entrance faces south, so the far side would be the north end of the station, where the steam engine has to be in order to leave the station.

If that's the case, wouldn't the far side be closer to the steam engine?

Since Harry dosn't understand when Ravenclaw is mentioned in Chapter 4, how does he know that Ravenclaw is a house?