Shape Tween
You can not shape tween library object or a grouped graphic
To tween a shape:
Click a layer name to make it the current layer, and create or select a keyframe where you want the animation to start.
Create or place the artwork for the first frame of the sequence. For best results, the frame should contain only one item (a graphic object or broken-apart group, bitmap, instance, or text block).
Select the keyframe in the Timeline.
Choose Window > Properties.
In the Property inspector, select Shape from the Tween pop-up menu.
Drag the arrow next to the Easing value or enter a value to adjust the rate of change between tweened frames:
To begin the shape tween gradually and accelerate the tween toward the end of the animation, drag the slider down or enter a negative value between -1 and -100.
To begin the shape tween rapidly and decelerate the tween toward the end of the animation, drag the slider up or enter a positive value between 1 and 100.
By default, the rate of change between tweened frames is constant. Easing creates a more natural appearance of transformation by gradually adjusting the rate of change
Choose an option for Blend:
Distributive creates an animation in which the intermediate shapes are smoother and more irregular.
Angular creates an animation that preserves apparent corners and straight lines in the intermediate shapes.
Note: Angular is appropriate only for blending shapes with sharp corners and straight lines. If the shapes you choose do not have corners, Flash reverts to distributive shape tweening.
Create a second keyframe the desired number of frames after the first keyframe.
With the second keyframe selected, select the artwork you placed in the first keyframe and do one of the following:
Modify the shape, color, or position of the artwork.
Delete the artwork and place new artwork in the second keyframe.