How to initialize a pointer from the IHttpContext interface?

Here is some of the documentation on this c++ interface: https://docs.microsoft.com/en-us/iis/web-development-reference/native-code-api-reference/ihttpcontext-interface. It is used to develop http modules and applications. The IHttpContext is just like it sounds; it contains information about the current request context such as the request or the response. They list several methods to get information from the IHttpContext pointer variable but they never state how to create one or initialize it with some context. Does anyone know how to create a IHttpContext pointer variable and initialize some members such as the request? Please comment if you do not understand the question. Thanks in advance!