In order to host your Notebook on GitHub, go to the GitHub website and sign up for a free website.
Once logged in you are provided with a website that can be added to. If you have development tools to use (git push commands are programmer commands to store files on a git server) you can do that or simply drag and drop your Notebook (ipynb) file onto your GitHub website.
I created an account there, with a notebooks directory, and placed one of the notebooks on that site. My GitHub site looks like:
I have added a small Notebook script there, and as you can see in the following display, the Notebook executes as expected: ...
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