First you download Tweener Class from here:
http://code.google.com/p/tweener/
Than you unzip the archive and copy it to your project folder.
Than you import it in where you need to use it:
import caurina.transitions.Tweener;
And than you use it, example:
mc.alpha = 0;
Tweener.addTween(mc, {alpha:1, time:1});
First I set the alpha of ‘mc’ MovieClip to 0, than I added a tween, a tween that [...]