Hi yankees660,
The serial code is located in the back inside cover of each ManhattanGMAT Strategy Guide. If you are having trouble finding the code, you might have purchased used books from a student who took a 9-Session Course. These students get their resources automatically activated online, so their books do not contain serial codes. Sometimes, they resell the guides on Amazon or other retailers, so just check to make sure that you didn't accidentally purchase used books. In this case, you can buy individual access to our 6 CAT exams on the
ManhattanGMAT Store.
Best,