No, bullet physics has nothing to do with it. Select the body part (either click on it or choose it from the items just above the top left of the document window which say a figures name followed by a body part) Now you can adjust it from either the parameters panel to the right of the display window or by selecting one of the tools from the tools panel to the left of the display window. These have bend twist and side to side movement tools. To use them click and hold on the body part and move the mouse.