So ...

Upon activation, simply create or edit your post or page.

You'll notice a new "Featured Video" meta box in your post or page editor:

As I mentioned earlier, all you need to do is to paste the video URL in that meta box. Here's the same meta box after inserting a video URL:

But there's a small trick ... Basically, the plugin replaces the standard featured image ... so you need to add a "replaceable" image (if you don't have one):

OK. Now let's see the result ... and some closing thoughts ...