How to create a win application that can interact with a website?

Hi I am trying to write a Windows application that can read the HTML content of a specific website and fill in some data in some input fields and send the page.
what I have done so far is reading the contents of the page from the object WebBrowser, going to the website.

I know that I need to create some request / response variables and work with them, but I do not have a good idea of ​​what I'm trying to do.
also my information about HttpRequestand is HttpResponseso small ...