In the Credit Card Payment Gateway, we need a separate email address (if you are also running the Salesforce_QuickBooks Solution for example) and the Merchant Services Providers (MSP) Integration URI - https://secure.authorize.net/gateway/transact.dll (if Authorize.net), the API Login ID (ex.  9V34QcfG) and the Transaction key (ex. 9j8aeC5c3m4TeJ88). These are entered in your Solution on the last page.