making a Movie Clip move across the stage

This is the easiest way to make a movie clip move across the stage

Open Flash and make a new movie, create a shape, a square or a circle, press F8 and choose "Movie Clip", now, select your new MC and add ths script:

onClipEvent(enterFrame){

  _x = _x + 10;

  }

and try it, you will see how your MC is moving, but it don't stop, it disapears from your screen, now i will explain why.

"onClipEvent(enterFrame)" this is the moment when your MC will start to execute the action adde after...

"_x = _x + 10;" this is that, it's X position will add it self 10 pixels, the continuos add of pixels will give us the effect of moving, tht's why.

Now we will make the MC loop into our stage. By default when you make a new movie this will be 550 x 400 pixels, using this parameters we'll make the loop. Select your MC and edit the script...

onClipEvent(enterFrame){
		 _x = _x + 10;
		if (this._x>= 550){
			this._x = 0;
  }
}

With the "if(this._x >= 550){" we are making that when it's X position is bigger or equal to 550 pixels, reset it's position to 0, else it will keep moving.

I hope you to enjoy this little tutorial, it may be useful for you, this a good start to make you understan how objets move by action script.