How to integrate a GPT/Open Ai assistant into your own website and how to build a paywall to monetize it?

How to integrate a GPT/Open Ai assistant into your website and monetize and how to build a paywall?? maybe with stripe?..I want to create something like studyX.ai in the educational field, but before to start to chat the user should decide the plan, something like this:

Could you describe me the correct steps i should follow?
if I knew Python well, the libraries, the connections with the API etc… would it be enough to build everything??
thank you