Perhaps break the project into steps?
Rig up the circuit that IanP posted, replace the relay with your DC motor, and see if you can get the motor to start going by simply shining your torch onto the LDR. You could prove this out on the breadboard. (remember to adjust the Variable resistor so it works when you want it too.)
If you are still having problems with the LDR, try getting the circuit to work by replacing the LDR with a regular resistor (try 1k ohm), that way at least you will know you have selected a suitable transistor and have it wired correctly.
Forget about getting the box part of the project going for now, tackle that when you have confidence in getting the LDR circuit to drive the motor.