Start with your circuit: power + wire + light sensor + wire + DC motor
Make 3 wheels. Trace a cup on cardboard to get perfect circles. What other objects can be a wheel? (Try a CD!)
Make the base out of cardboard. Cut a slot in the cardboard wide enough to fit the wheel.
Place modules on cardboard base. Use tape to hold the modules down.
Add wheel to the motor mate. You can use a pen to poke a hole through the wheel where the motor mate will go. Then place the motor mate onto the DC motor.
Poke skewer through two remaining wheels and glue them in place. These will be the back two wheels. The skewer will be your axle.
Now attach the back wheels. Cut a rectangle out of paper and fold it in half. Them place it over the axle and tape it down. (Tip: don't make it too tight. The axle should be able to spin.)
Time to drive! Optional: Draw and cut out a figure of your self to attach to the three wheeler. Now you have someone to drive it!