There are two possible reasons why you may not see the customize option on your subscription in your account:
1. If you have a cancelled subscription that does not have any credits available or a gift subscription that has ended, you will not be able to select any Add-Ons. You must have either an active subscription or a subscription with available credits to add Add-Ons to your subscription.
2. Add-Ons are not available yet for the upcoming month. Once Add-Ons are available for an upcoming month, we will notify you via email. At that time, you will be able to go to your Account, select the Customize button on your subscription, and add Add-Ons to your subscription.