Arduino Mega2560 Manual page 26

Prepare a black track (the width of the black track must be between 20mm and 30mm) in
white ground. Please be noted that the bend angle of track can't be too sharp otherwise
the car will move out of the track.
Turn on the car and put the middle of tracking sensor module facing over black track, and
then the car will move along the black track automatically.
Youtube Video Link: lesson3- https://www.youtube.com/embed/NTqsy7HClZc