Create The Shape Tween

In the old days of hand-drawn animation, a lead animator would create the main drawings in a cartoon. Then, other animators would take those key drawings and create a smooth animation by hand-drawing all the frames between them. Now you're the lead animator! You are create the Keyframes and let the Flash software compute the differences between the keyframes. In Flash, this process is called tweening.

To start, select any one of the static frames between the two Keyframes:

Now look for the Properties box at the bottom of your screen. Use the Tween drop-down-list to change from None to Shape:

Check out your timeline again. It should have a green background with an arrow leading between the two Keyframes. Those aren't Static Frames anymore, they are now part of the Tween:

Save your work! Then, test your animation by using the keyboard shortcut CTRL+ENTER: