Well Mr. Cubecolour thank you so much for you reply, I made it by adding the extension of html in Dashboard, Network Settings, and Upload File Types.
It was a good experience for me to learn and to search about it, i am amazed that it is too much easy to upload an html file without using any plugin.
Secondly I am working for a newspaper and I want to manipulate all the newspaper pages in a single webpage to uploaded like an epaper so i am wandering to learn more and more and getting experiences.
Once again Thank you so much sir, have a nice day and stay blessed, 🙂