CNP currently does not offer membership upgrades. Once you pay for your membership, it will remain that membership option for the year. Once your membership expires, you are free to upgrade.
Once inside your account, click the arrow near your name in the upper right-hand corner. From this drop-down menu, click on Subscription. You will then see a Cancel Membership option in the bottom right.
If you change your mind and would like to resubscribe, login to the CNP Library Membership home using your same credentials. You will then be prompted with an option to resubscribe.
At present, membership are set to automatically renew at the end of your yearly subscription period.