Go to Configuration > Payment and Shipping Gateways and click to edit PaymentSense.
Enter the various acccount details given to you by PaymentSense. You may have both test and live account details, so ensure you don't mix these up. We suggest first configuring the test details, setting the status to 'test' in Kartris (this will only show the payment option for PaymentSense at checkout if you are logged in to the site as an admin) and then running through some tests with the test card details available from PaymentSense.
In older installations (up until Kartris v2.9012), the hashmethod was hardcoded into the plugin as MD5. From v2.9013 onwards, the default is SHA1, though this is changeable through a new setting called HashMethod, within the PaymentSense settings in the Kartris back end.
The PostURL may be different depending on which processor you signed up from. This is the location of the payment form on the vendor's site where the user is redirected in order to make payment.