WordPress.org

How can I tell if it is working?

You'll see a new button at the right end of your Post Editor toolbar

I don't see the new button

1. Have you verified that you activated the plugin?
2. Are you using the Visual Rich Editor?
3. Check Users -> Your Profile, the top checkbox should be checked.
4. You may need to clear your browser's local cache (ctrl-F5 in Firefox, for example)