While in the app, click “More” next to “Your Apps” at the top right corner of the page. This will take you to your App Center. Locate High 5 Casino and click on the gear to open the settings. A new screen will appear. Scroll down and uncheck the 'Post' option in the 'This App Can' section.
If even this is too much, simply go to the latest post by High 5 Casino on your wall. Click the 'x' icon at the top right of the post. Next, select “Stop Publishing Activity from High 5 Casino” and confirm your request.