Thanks for the question.
This is to associate the courier integration with the “Courier” that exists in your account. If the courier you need doesn’t exist in your account, you need to create it first at Settings → Delivery settings → Couriers you use.
This is essentially the first step in the Integrating couriers for shipping label creation & tracking of deliveries within Breww help guide (“Enable couriers you use”).
If we can help any further, please let us know.