Hello,
To move a circle along a path create a circle shape layer. Then with the shape layer selected grab the pen
tool and draw the path you want the circle to move along. Now open the shape layer, select shape 1,
select path 1 and click on path then cut it in the edit menu. Now open the ellipse you created and select transform, click on position and paste. Select the anchor point of the ellipse while at the first keyframe that was created when you made the path and move it to where you want the start point to be.
Hope this helps.