Occasionally you may want to taxi your plane on the ground. You might be making your way to a runway for take off or clearing the runway just after landing. Using rudders, you'll control the tail fin, plus the front wheels. To move, your generally accelerate the throttle to get moving then ease off to roll forward. When moving on the ground, you'll also want to make sure the flaps are retracted to limit your plane's lift.
Brakes are also helpful to stop or slow down for turns.
Take off Taking off is probably one of the simpler things to do in a flight sim. You basically keep the plane in the middle of the runway using the rudders and accelerate until you have enough lift to get off the ground. If you're using a big or heavy plane, you may want to extend your flaps some to get extra lift. You'll want to take off the breaks, and then accelerate the throttle to full power. When going down the runway, you'll want to watch to speedometer until the plane reaches an adequate speed to take off.