Trouble bending an arm at the elbow once subdivided I subdivided the arm at the elbow. Yet when I try to bend the arm at the elbow to move the elbow back, the shoulder moves instead. I am trying to position it like the arm drawn on the right.  Please help if you have any advice to get the arm to bend at the elbow. I am very very new to this.  Thank you for any help you can offer.
First you need to disable Limit selection to visible to see through the mesh, then select only the vertex of the elbow to bend the arm.