It should be as simple as breaking up your existing HTML into proper chunks that you can include (header, footer, sidebar, etc). Then you’ll replace the content itself with WordPress loops and transfer all of the content into WordPress’ posts and pages.
Definitely recommend doing it this way even though I think there are better CMSs out there.
I’m sure there are a ton of resources out there for this, none spring to mind immediately.
The videos on this site!
