Access codes are only complimentary and found within eligible new purchases of eBooks as well as printed textbooks. If you have not purchased a new copy, then you are not guaranteed a complimentary access code.
These may also not be purchased separately. If you think you need an access code, then it is likely that you need to purchase Course Only Access during the enrollment process. This will provide you with access to your assignments, but does not include the eBook.
If you have purchased a new copy and still have no access code. Please contact the institution you have purchased the text from and verify it's a new purchase.