You know how to open the case right?
More than likely it's pretty easy. Mine is just one handscrew and a latch, yours may be different.
Open up the case, unscrew the optical drive, disconnect all cables (make sure you know where they go for the future), and at the back of the drive, you will see little pinholes and a white thing. Sorry, i can't describe it that well, here's a pic:
Do that exactly, and make sure it's set to Master.