To finish this project in a week is pretty optimistic for someone with no Arduino experience. It might be time to ask your teacher/professor or a classmate for help. Do you have any experience with any other microcontroller/programming language? Maybe it's best to try it with something with which you have experience. Hopefully you do have some programming experience and you'll be able to google around to find some line follower example code. Certainly, there is enough around. You can mix, match, and adapt those examples to your project. http://lmgtfy.com/?q=line+following+robot+arduino+code
You may not get all the help you think you need on forums when you say you're working on a school project due in a week. It implies that you have procrastinated and wish someone to write the code for you.