A processing account is an attribute to configure different business and processing rules for the terminal and currency, like which authorisation type is used (final, pre), whether to use 3DS for customer present transaction, which payment methods are allowed, whether some capture delay is set etc.
Processing accounts can be found in Merchant Portal and they look like this: EUR3D1 or USD3D1.
1. Sign in to the Merchant Portal
2. On the left side menu, select Processing Accounts