Hey there,
I think Elementor only accepts templates in .json format, so you should convert your html&css&js code to .json format and then you can include your code to elementor.
Here is how you can convert your html page to json:
https://stackoverflow.com/questions/52634857/how-can-i-change-the-form-of-html-css-to-json
PS:I never tried it so i am not sure.