configure gateway properly for refund, quickpay development

in Your manual p. 403 you state:
If your payment organization supports remote refunding and your CBSubs™
Payment Gateway has been configured properly, you should see a Refund button in
the status column of your Payments as illustrated in Figure 171.

looks nice in the figure, but what is "configured properly"? I don't see any refund button although the gateway supports remote refunding. Payment is completed with "notify" and autorecurring.

also :
I really need documentation (which functions and classes handles which features) for the admin payment/subsciption handling functions .
Where to find this?

Depends on the gateway, but typically there will be parameters to supply API credentials to enable refunds from within CBSubs. However our Quickpay gateway does not include an implementation to refund from CBSubs.

I really need documentation (which functions and classes handles which features) for the admin payment/subsciption handling functions .
Where to find this?

In the code it self. Nearly all of CB and its plugins utilize phpdoc. Using an IDE you can review the functions available to the gateways payment class. Specifically the function refundPayment handles the refund API calls.