It doesn't get any simpler than this :-)
Click on the text (either the title or the description), and you can begin editing immediately. As soon as you tab away, or otherwise finish editing, the OCP manager will update the text on your published pages.
There's no apply button. Nothing. It just works!

You can change titles & descriptions before or after you've published.
While you can change the title after you've published, there's one thing you need to be aware of. The published URL.
The URL that people use to view your video is made up from your title. So, for the above example, the URL is (this URL we've used here is for example only, it won't work if you type it into a browser):
If I then change the title to something else, you can see that the URL changes as well.
http://media.shinywhitebox.com/neil-clayton/some-things-to-try
Keep this in mind when you're changing the title of an item. It really doesn't matter that much most of the time - because if a user visits an old URL that doesn't exist, they will be taken to your index page where they can find the video.
It does matter for embedding though: If you embed the link to the video, and then change it's title, your old embed code will no longer work properly.