Go to http://knitcamp.oliveknits.com/ and once logged in, click on the hamburger menu (stacked lines) on the right to open it, then click the gear icon "Settings" at the bottom of this menu. This will take you to a page about your Subscription & Account settings where you can cancel your subscription, change billing details, and update your email address.
NOTE: In the mobile app, under settings, you can view your subscription, push notification settings, and change your account name, but NOT your email address.