If you are a first time user of Critical Pass, you can register your app account at https://web.criticalpass.com/customer-register.
You can find your Order ID in your confirmation email. Please note that you'll need to use the same email address to sign up that you used to make the initial purchase.
Once you click the "Register" button, your account will be created with access to the materials you purchased.
If you are a repeat user of Critical Pass or are adding an additional set of flashcards to an active account, you'll need to instead need to sync the purchase to your existing login. You can do this via the Account Status page, accessible using the blue profile button in the top right of the web app (or at https://web.criticalpass.com/dashboard/account/status).
Just enter your Order ID in the field and click "Sync."