For starters, go to "Subscription" which you'll find under your workspace name in the top left corner:

At the bottom of the page, click Cancel subscription:

• If you cancel your subscription in the middle of your billing cycle, you will have all the benefits of the subscription until the end of the billing cycle you have already paid for.
• Your existing files and content will not be deleted, so you can restart your subscription at any time.
• If you've added new editors during your current billing period but cancel before the next invoice:
  • Monthly subscription: We’ll send one final invoice at the end of your subscription
  • Annual subscription: The final invoice will be issued a month after your cancellation