How do I fix a arm to a body?

Hi guys I am using the Robot template in Ch the one walking constantly to the right..

Now I have made my own arms legs torso etc in photoshop and they are working perfectly fine..

However the new arm I have created isn't staying fixed to the shoulder on the torso.

Its swaying slightly left and right (sliding across) the torso.

I have used the pin tool (fixed handle) where the arm meets the shoulder torso but its still sliding left and right around that area..

How do I make it fixed to the body and allow it to move with the body as opposed to slipping across.

Cheers.