That looks pretty good for a start. Next, I’m going to create a child theme before making any other changes. This is rather technical and not required but it’s recommended for various reasons as explained in the WordPress codex entry.
Having created the appropriate folder and files, it’s a simple matter to activate the new theme. There is no image associated with it yet so I’ll go ahead and take a screenshot and place it in the child folder per this page.
Refreshing the page and voila, the new theme is active and working fine. Time to test the CSS editor just for grins. Changing the background color is trivial and working fine (although using the example from W3Schools is quite ugly it gets the point across):