Movie clips are a bit different from regular symbols. Instead of operating on the main scene's timeline like a regular graphic symbol, they have their own timeline. Theoretically, you could place a movie clip on a single frame in a scene, and then load the SWF and have tens to hundreds of frames of animation inside a movie clip playing on that single frame. Movie clips let you make movable animation--you can animate something as a single entity, and then drag that entity around and manipulate it inside the scene.
To start with, we'll go back to the left arm and unlock the layer--I tend to lock my layers every time I'm finished editing them, to prevent making any mistakes during each progressive step--before double-clicking on the left arm itself to open up the movie clip symbol. This should grey out the rest of your scene and leave you with the three separate parts of your arm to edit, and a timeline that affects only this symbol. Remember, this is a nested symbol, so there are only two parts: the upper arm, and then the lower arm and hand joined into a single symbol. Your next edits will move the lower arm and hand together, as part of a single unit. We'll step down in iterations to the individual animations.
