You can scrub your timeline to see how the movement of the forearm will look, but in order to view the entire thing with the movement of the entire arm, you'll have to preview, as the motion of movie clips doesn't show up in the main scene. You should have complex paired motion akin to the image above.
Next you're going to go one level deeper and, while inside the symbol for the arm, double-click on the symbol for the forearm to get inside of that. On this level you'll animate the motion of your hand only; I'm not going to walk you through it again as you should have the hang of it, but remember to move your pivot point to your wrist. For a bit more natural movement, try to time the most movement of your hands with the pauses or smaller motions of the forearm, while they may stay still or only move a little bit while the arm is swinging in larger arcs.
