3) Select the planet layer. It is important that the planet layer is selected so the motion guide layer is created on top of that layer.

Select the motion guide icon at the top of the document. See the picture below. Click where it says Add Motion Guide.

Now, let's get that planet rotating around the sun. This is tricky so may need to repeat these steps several times.
4) Select the circle tool.
Select a white stroke.
Select an empty fill.

5) With the guide layer selected, draw an ellipse around the sun.

6) Select the eraser tool.

7) Erase a very small part of the ellipse.

8) Select frame 1 of the planet layer

9) Move the crosshair of the earth to the beginning of the ellipse.

10) Select frame 50 of the planet layer.
11) Move the crosshair of the earth to the end of the ellipse.

12) Drag the playhead to see if the correct connections have been made. The planet will follow the ellipse if it is correctly placed.

13) Test your movie.
>Control
>Test Movie

If your sun just appears for a second, do the following.

((note: First time only:!!!
Select frame 50 of the sun layer if it is your first planet to rotate.
>Insert
>Frame
This brings the picture into all the frames.))