How Do I Make Rotating Arms?

Hello, Look, first impression this probably seems like a lazy question, but trust me, I have done research. I know that to rotate I would probably have to rotate around camera to where the camera's rotation is and that I need the sine of x and the cosine of y, but I still can't get it. Can someone please help me in getting arms that rotate to wherever the character is looking? What should I do? I'm not requesting, I'm just asking for hints or help. Thanks for reading.