Assuming that you are talking about the QC Open Test Architecture API. You can access that documentation by logging into your QC project or Site Administrator then select Help > Documentation and read the OTA Guide.

It is a COM API that can be used to allow the integration of any third-party tool within Quality Center. Additionally it is a manipulation API that permits interaction with the Quality Center application directly through programatic means rather than through the Quality Center Client GUI. The COM API is a dll. It has one entry point.

Wrappers are not technically ''Supported'' by HP, that would assume that they had developed them. That being said, there have been several people who have written Java classes to ''wrap'' the COM API. A Typical approach is to use one of the Java/COM bridges like these J-Interop, Jacob, Java2Com, EZJcom, Com4Java. That's not to say that's the only way.