You can start as soon as your Workit account is active. After signing up, you'll receive an activation email to set up your account and password; you then log in to the app and can book your first workout straight away.
Does something seem to have gone wrong with your start date, or did you receive nothing after signing up? Let us know. We can adjust your start date if needed so you don't miss any days of your subscription, and check whether the activation email was sent correctly.