Perhaps a picture would help a little! I have no desire to add confusion, but rather to remove it.
In the picture below you are looking from the stern towards the bow (Funnel on starboard side) If you have the Funnel on the port side the right hand wheels are for the engine which is now the forward one, otherwise the instructions are the same.
The two controls on the left are for the forward engine and the two on the right for the after engine. you can drive the ship with one engine or two. Two engines give maximum speed of course. If you turn the small wheel clockwise the ship will move ahead, anticlockwise she will move astern. If you turn the big wheel clockwise the ship will turn to starboard, anticlockwise she will turn to port. When you add power from the after engine the controls for that engine will do exactly the same. (Just imagine the yellow arrows are the same over the right hand wheels.) As sadsid says, quoting Marty (mvsmith), it is probably better to drive the ship with the mouse as you have very much more simple control. Ballast also thinks this is better too. These instructions are for players, like myself, who do not have any fancy controllers, but merely a mouse and keyboard to play the game.
Traddles.
N.B. Sadly the Youtube video mentioned in JoMach's post has been removed.