I have a designed theme in html and i want to upload that whole theme in WordPress of my website.
As far as I know a wordpress theme is just not built with HTML & CSS,
You would have to build it with PHP for example (not sure if there’s other options) and use their functions, handles etc to be able to make the theme integrate correctly with front-end, the posts, pages etc.
Have a look at the following:
You can use WP coder plugin