How do I stop my puppet arm from stretching

You mentioned you cannot find the arm ik. Arm IK is an extra behavior you have to add yourself  - oksamurai had a great video on how to use it somewhere. There are some common gotchas (like the shoulder tag has to be on the body, not on the arm)

Arm Ik will only work if you have everything tagged (elbow, wrist, right and left shoulder). If it can't see all the tags it requires, the arms will remain stretchy.

Hope that helps!