There is an Open Test Architecture API reference document available within the QC product. Log in to a QC project and then select Help > Documentation Library. You may need to download the file to your local system to open it. The document includes many examples for using the API. These examples are not specific to using the API from QTP.
The object used in a QTP script to interact with QC is called the QCUtil object. Look it up in the QTP documentation for more information.
If you want training on how to integrate QTP with QC, or the QC API in general, I suggest you look online for training resources. This is more a forum for dealing with specific situations rather than a training resource.