Frappe - Payment integration

Hi,
I go through this link
https://frappeframework.com/docs/user/en/integration/razorpay#include-checkout-script-in-your-code

In frappe i am using web page i can create html page and i can call custom-api in the api.py file…

But how to do this integration. Anyone please explain how to do this. I can’t get a point.

Thankyou