The InstantEStore's shopping cart is integrated with PayJunction. Simply select PayJunction as the Payment Gateway and provide your PayJunction QuickLink Login and Password.
QuickLink API Login and Password
To see how to set your QuickLink API login and password, click this link:
If you need additional assistance, the following link will help you setup InstantEStore with PayJunction: http://www.instantestore.com/contact_us.cfm