This sounds like an inverse kinematics function. You know where the "end effector" (in this case the end of the stick) is supposed to move and what its orientation is, and you want to know the joint angles that will result in that motion.
Take a look at this page to learn more about inverse kinematics in Simscape Multibody. In it, you see how to find joint angles for individual arm positions. If you want the arm to follow a trajectory, you can find the joint angles for a series of points and smoothly transition betweeen those joint angles.
--Steve
