Hi raunaqkapoor,
If the activation code has already expired, then you likely won't be able to use it. That having been said, IF you bought the book NEW (meaning that it's not a used copy - and that someone else has already used the code), then you might be able to contact Wiley to explain your situation. You might be able to convince Wiley's Customer Service Team to give you a new code/access.
Before I can offer you any additional advice for your studies, it would help if you could provide a bit more information on how you've been studying and your goals:
Studies:
1) How long have you studied? How many hours do you typically study each week?
2) What study materials have you used so far?
3) On what dates did you take EACH of your CATs/mocks and how did you score on EACH (including the Quant and Verbal Scaled Scores for EACH)?
Goals:
4) What is your overall goal score?
5) When are you planning to take the GMAT?
6) When are you planning to apply to Business School and what Schools are you planning to apply to?
GMAT assassins aren't born, they're made,
Rich