Doing it! - Shape Tween

Select a stroke and fill color.

Select the circle tool from the tools panel.

Create a circle on the stage in the upper left hand corner.

Look at the timeline and note that in frame one, there is a dot. That is a keyframe that was automatically created when you made the circle.

Double click the words "Layer 1" and type " circle to square".

Click in frame 30 of the timeline. Go to Insert on the menubar and Insert Keyframe.

Select the Arrow Tool from the Tools Panel, click on the circle and delete it.

Select the Square Toolfrom the Tools Panel and draw a square in the lower right hand corner.

Now, select the entire layer, either by clicking on the words circle to square once or by clicking anywhere in the area between layers 1 and 30. You'll know it's selected when the segment turns black.

Go to Frame Panel and choose Shape next to Tweening.

The Timeline will look like this:

Grab that red bar and move it back and forth along the timeline. Watch what happens to the ball! All the "inbetween" frames are now drawn. You can also hit return to "play" the timeline.

Want it to take a longer time? Drag the keyframe (the dot) from 30 to 60.
Play the timeline now.

Note: If you're using a shape that has been converted to a symbol, you will have to "break apart" the symbol for shape tweening to occur. Just select the symbol, drag a it to the stage, go to Modify - Break Apart. The original symbol in the Library will NOT be affected!