To update or change your subscription, click Profile on the main menu and then click Membership on the horizontal menu.
On the Membership screen you can select to change your subscription level to either Monthly (which costs $3.99) or Yearly (which costs $39.99). Payment can be made either through credit card or through Paypal.
If you wish to cancel your subscription, there is a Cancel Membership link at the bottom of the page. Clicking this will take you to a confirmation that will allow you to cancel your subscription. If you cancel your subscription, you will revert to having access to only your own diary, and will not be able to add new entries or note other users.