If you are visual guy you can watch this tutorial in video mention below this lesson.
In this tutorial we will see how to interface photo-resistor sensor with LED light. If you have not read my previous article for photo-resistor in Arduino. You can click here.
Do connection as shown in circuit diagram. Whenever light fall on sensor it will create high resistance and prevent to flow current. And LED light will OFF. When there is no light on sensor it will have less resistance and current will flow and LED will ON. All the parts and programming is same as previous video. Only for this you will need one LED light and 2 Extra jumper wire.
When I fall light on sensor LED light will OFF. When I move light from sensor it will again ON.
Components list for buying online.