Log in to the BS PAYONE Merchant Interface at https://pmi.pay1.de/.
Configuration > Select payment portals. Then click on “edit” at the payment portal of the type “Shop”:
Under the tab “API parameters” the fields Merchant-ID, Portal-ID, Key and Account-ID can be taken.
These values must be inserted with AlltoBill on the settings page of PAYONE (Settings> Payment Providers> BS PAYONE):