First thing to do is, Right click on the ball, and Select Edit in Place.
Now, depending on what your wanting to add depends on how you'll add it. For example if you already have an animation done and you want to import it, Create a new MC, and Call it Import (or what you want to call it, For this tutorial we're going by Import).
After importing your animation, move it to the New MC you made. then, Place the new MC called Import into the ball MC. Don't forget to center it and or place it where you want it.
Then you'll need to test it.
As for making a new one it is simple. For this tutorial we'll make another circle that goes around our Big Circle (ball). We'll make something similar to the image on the right.
First off, Make sure you have a New Layer.. Name this Layer Ball 2.
Note: make sure That the original ball layer is on top of the Ball 2 layer
Next, with the Ball 2 layer selected create a Smaller ball shape that what your original ball is. Kind of like the image above the timeline.
Select the Smaller Ball and go to MODIFY > GROUP or Press CTRL+G. This Groups the small ball together so that we won't hve to make it into a symbol/graphic, just to animate it.
After you have the small ball made, Select Ball 2 Layer, and Right click on it and select Add Motion Guide.
Select the Guide layer, Now Create a Circle with No-Fill. Then Select the Circle you just made, and go to the 'Free Transform Tool' and Make it an oval and Center it like the image on the right. Lock this layer.
Then take the Circle you made and Place it on the Line. It should SNAP TO. [This needs to be centered on the line other wise the Guide Layer won't do its job.].
Next.. Select frames 20 for All 3 Layers and create a new frame for each (Insert Frame), Then Right click on the Ball 2 layer, and Insert a Keyframe at 1 & 10. And for Frame 1 & 10, put an Motion Tween on each of them.
Select Frame 10 of the Ball 2 layer, and move the ball to the opposite side of where you started. From here Hit ENTER this will play run the tween so you can see it's movement. If the ball only runs half the circle then goes back the ways it came from you'll need to adjust Frame 20. Per say your making your ball go Counter Clockwise, and it does not complete the circle, You'll need to move the ball on Frame 20 to the left of the starting ball on Frame 1. then hit enter again.
Now, Exit the EDIT IN PLACE. To do this Click on the Scene 1 text (this may be something else if you had renamed the Scene from the start.)
- Part 2
To Test this hit CTRL + ENTER.
If you have any questions or problems regarding this please let me know.