You may need to check the information sheet of your potentiometer, however it should have three legs, a power leg, a ground leg and an output leg. The middle leg is usually the output leg.

Using croc clips, connect the power leg of the potentiometer to the PWR leg on CodeBug. Now connect the ground leg of the potentiometer to the GND leg of CodeBug. Finally connect the output leg of the potentiometer to leg 0 on CodeBug.