If we need to make something be in a particular position based on some code, such as the rudder of a boat, the steering angle of a car, the openness of a window, or the direction of a solar panel, then we can use a servo.
Servos provide a way to request a position from 0 - 180 degrees. The request is done using only one IO pin, so you can control up to six servos with the Magnolia without adding any other chips.
No biggie for this one, just open up the example sketch found in File > Examples > Servo > Sweep
Change the pin the servo is attached to by changing this:
myservo.attach(9);
to this
myservo.attach(A0);
Now you can upload and wire it up.
Servos have leads with three wires. One is GND, one is VCC, and the last is the signal wire, SIG.
As soon as you connect VCC, the servo will probably squeak. When powered, the servo will try to go to wherever it thinks it should for a moment, and that could be anywhere while it is powering up.
As soon as you connect SIG to A0, the servo should rush to wherever it is meant to be, then continue to follower the 0 - 180 - 0 degree sweep that the Magnolia is looping through.
You could try combining the analogue input lessons with the servo, and have the servo react to the potentiometer, or light levels.