Hello @SantaCode You would just map the joystick button to the function which handles the movement of the joint while the joystick is being rotated.
if (joystick) { if (buttonA) { // movement for limb } }
You would need to code the part of the arm to rotate at the point of the joint connection based on the joypad direction.
shoulderJoint.setRotateValue(var);
You need to feed the y and x for the joystick which will give you the radiant value, then you can convert it to degrees to feed into the function. I don't know what library you're using however, but SFML for example requires degrees.
http://en.cppreference.com/w/cpp/numeric/math/atan2