Start a new Flash CS6 movie.
Becaseu you can't constrain the last joint in an armature, we will add an empty movie clip after the hand. Later we could edit that movie clip to put something in the hand.
Using the brush, draw the 3 arm parts and an object held in the hand, as shown below.
Select each section and make it a movie clip (F8). Name the movie clips UpperArm, LowerArm, Hand, and an object in the hand (it can be an empty movie clip.)
Select the lower arm and put it on top (Modify, Arrange, Bring to front)
Drag the pieces so that they overlap slightly:
Double click the lower arm segment and use the brush to cover up the line at the top and bottom edges.
When you go back to scene1 the arm will not show the edges: