Adding grav powered blog to static site

I have a one page scrolling static site that I'd like to add a grav powered blog to. But I'm not sure the best way to do this, as I don't want to have to convert the homepage. i just want to leave that as is and add the grav blog onto it. Can someone advise me on the best way to do this?

Simplest thing: download the "Blog Site" skeleton.

Create an empty page in user/pages/home/home.md
Make that your home page in the System config.

Make a user/themes/antimatter/templates/home.html.twig file, and paste in there the whole static page you already have. That will serve your page as-is (just make sure the CSS/JS paths are still working), and add a link to /blog.

If it helps, here's the process I used to migrate a HTML theme to Grav