The process of tweening in FLASH is a time and effort saving aspect of animation that Flash uses to fill in frames of animation from a starting point to an end point during an animation.
Tweening creates remarkably continuous transitions.
Tweening can also involve the transformation of shape and colour of an object during the transition.
Use this tutorial to refresh your skills in the basic process of tweening.
                                                Tweening means to fill the frames (cells) between
                                                Onion Skinning means to view each frame in the tween

Open Flash

Create or import an object in a layer that you want to to the stage

Use the select tool to select the object (this must be done or the tween won't work!!!)

Insert> create motion tween

Tweens can occur simultaneously in many layers at the same time!!

Insert> key frame
(you can right click this op)

Move (using the arrow tool) the selected object to the final position of the tween transition.

An arrow should appear in the timelines bar that starts at the first frame and points and stops at the last frame.

Onion Skinning

You can observe the transitional stages of the tween by using the onion skin function

Onion skinning allows you to view the transition and make plans for modification