Follow these steps if you received a code for a free trial:
Cleeng (paywall software) created this video tutorial that also might help you.
To view and or update your account details, click My Account in the top menu, then click My Account again. Here you will be able to view your purchases and subscriptions, update your personal info, and update payment details.
It looks like this:
Click on the My Account in the top menu, then click My Account again. Go to the “Subscriptions” tab and click “Unsubscribe”. Then select the reason you are unsubscribing, and click unsubscribe again.
Go to these links for tutorials: