PID Control on Sun Tracking

I need suggestions on how to implement the principle in these videos.

By having the DC motor’s position to be controlled thru PID control. I want to apply that to sun tracking by connecting two photoresistors in the motor’s potentiometer. When the arduino detects that the values in the motor’s pot is not equal to the desired position, the arduino will command the motor to move until the desired value is achieved.
Here is the schematic diagram provided in the second video.

And also I will only use arduino uno and the l293d shield