I just applied for a Revecom account (Paysystems) to process payments for one of my websites, however I'm finding it very difficult to find any technical documentation on using their system. The PDF docs they have don't go into very much detail on how to use the Postback system (or how it really works) and there seems to be no documentation anywhere on using their admin interface and what certain features do (PIN codes, how to test, authenticating payments, return url vs postback url, etc).

Am I missing some simple link that leads to explanations and documentation for their service, or do I have to go through their support crew for any technical detail I want to know?