Creating An Alpha Tween

How to create a alpha tween:

Insert a keyframe into the main timeline at frame 24.
Then insert a keyframe at frame 12.
Go to frame 12 select your movie clip object then change the alpha setting to "0%" in the properties panel.
In the main timeline right click between frames 1 and 12 and select "Create Motion Tween".
Right click between frames 12 and 24 and select "Create Motion Tween".
Then in the main menu go to Control > Play to play your animation.

Note: Make sure the bitmap has been converted to a graphic or movie clip symbol before trying to create a tween.