Like you see here, the red dots only represent the joints in the model file. What you wanna do is add a body to each part of the model that you want to have a seperate section that can move, then link those bodies together using the Joints tool. Most likely you wanna use JointHinge for most limbs, but maybe a JointBall for the neck to head. Just be sure to set the proper Min and Max angles so that the limbs don't bend in the wrong directions. It will take some time, but this screenshot is of the first and only ragdoll I've done, and I think I spend about 30-60 minutes on it.