You should use a joystick with a twist handle. Then you kan use that as a ruder. You can also assign the ruder movements to the joystick or to the arrow keys. You should look at the control assignments in the settings. In standard settings, I think it is somewhere on the numeric part of the keyboard, but you can find that easily in the control assignments. The twisthandle is much better though, as controlling the aircraft is much easier. The best is some separate rudder pedals, but that's of course much more expensive.