how to pass value to website textbox using WinInet, winapi?

I want to send value to website and want website response to me. A Website that I will use have a textbox. But I don't know how to send value to textbox in window application. I can receive HTML using internetReadFile function. but I cannot do anything with HTML. My ultimate purpose is sending data which is I insert in textbox IN WINDOW APPLICAITON and receiving data which is if I insert data to textbox IN WEBSITE, website returns. I'm using C and WinInet api THANKS!!!!!!!