I think the easiest way to integrate the the two for you would be to add these tables to your existing db, but when you add it to your site you should put it in it's own directory. You will still need to configure the globals and connection info for the PowerCMS files. If you do it like this you will have a PowerCMS implementation that will be separate from the PowerStore but you will be able to add the content to any page in your site since it uses the same db.