NOTE: All of these steps must take place on the same layer.
You must change the name of the layer to avoid confuse.
motiontween1.gif
Draw any shape you want.

motiontween2.gif
Insert keyframe in any frame you want.

motiontween3.gif
Move your shape with selection tool.

motiontween4.gif
Select layer with subselection tool.

motiontween5.gif
Right click on the frames and select “Create Motion Tween”