With most Genesis themes, you actually don’t have to set the homepage as a static page, you would leave it at the default “Latest Posts” in Settings > Reading. The home.php file in your theme will automatically be detected and used as the homepage.
For the blog, you would simply create a new Page and name it Blog (or whatever you want) and then select the blog template……then add that link to the menu. That’s how the demo is setup, right along with all other Genesis themes.