Some planes need rudder input to make a smooth, on-track turn. When turning, a plane can follow the nose, or the tail can skid to one side or another, usually to the inside of the turn. This is also called "adverse yaw" and can be caused my the "down" aileron having more drag than the "up". Use the rudder in the direction of the turn to bring the tail more in line with the nose. It usually doesn't take much. Practice with it until your plane is making on-track turns.

Dr.1