ORIGINAL: gaRCfield
I believe it is never too soon to start using rudder. Like I said, start playing with it as soon as you are comfortable flying the plane. Try making 'flat turns' (steering with the rudder and keeping the plane level with ailerons). You are using a sim, so you can start using the rudder now! That's what I did, and my instructors were amazed when I was landing on my third day of flying and using my rudder to steer the plane onto the strip.
This is a golden piece of advice! I cringe when I hear/see 'soloed students' fly without using rudder. It MUST be used in all phases of flight (for the makings of a good pilot) ... After lift-off, in flight and on final approach.