One click from your dashboard. Settings, Billing, Cancel.
What happens after
Your subscription stays active until the end of the period you already paid for. You do not get charged again. Nothing is shut off immediately.
After the period ends
Your public page goes offline. Your account is not deleted, your data is not deleted. You can resubscribe any time and pick up exactly where you left off.
To fully delete
See Delete your account. Cancelling and deleting are different actions.