This is an area where I tend to fall short when I'm rigging, so when it came to putting the joints in the arms, as well of the relevant controls, I would have to follow the relevant part of the Digital-Tutors tutorial to the letter.
Of course, I will now need to make sure that these joints are inside the arm and also positioned in a way that it wil bend accurately. In this video, I found that the joint was actually outside the arm, so I just repositioned the joints, similarly to how I did the leg. See this video.
Another important part was to make sure that the local joint rotations were all in order and that they were all straight. I did this by hitting Fn and F8 to check the rotations of the joints. As you see below, all of the joints in the forearm are straight as they are all aligned with the X, Y and Z axis perfectly.
How I did this was by clicking the starting point at the shoulder and then clicking the forearm to insert the handle. Even though this handle was not going to impact on the wrist, it would need to be located at the wrist; as all of the controls for this arm would need to be based there.
In this video, you will see me relocating the effector to the wrist, using the Hypergraph.
Now, I can use the IK handle to move and bend the arm. It is an IKRP so this means I can rotate the arm in several directions.