You should have 12 vertices around the beginning of the arm. You can now either extrude the four faces or look at Illustration 2.
Create new edges near the wrist (Step 2).
2. In the hypergraph, middle mouse the armR_IK1, armR1 and armR_FK1 joints under the armR_Gimble (Figure 18) so that your hierarchy looks something like Figure 19.