If steering wheel is rotated in clock wise, oil is pump out from the port (right port from the front view) into the port of cylinder (Port side).
This cause the cylinder tube move to the port side, which move the boat to right side (starboard). Oil displaced from the opposite end of the cylinder flows back to the helm pump.
For steering in the opposite direction, simply turn the helm pump the other way.
When no course corrections are required, the inbuilt lock valve holds the outboard engine stationary.