Now that you understand simple single trait or monohybrid crosses, we're going to kick it up a notch and look at dihybrid crosses. These are crosses that look at two traits at one time.
Start by watching this video, Dihybrid Punnett Square. Try writing this down on your own paper while watching the video, it will help you know what to do on the assignment.
The Biology Corner, also has a good page explaining Dihybrid Crosses.