How to remove a Facebook page application
Uninstalling an app from a page is easy.
Step 1 - go to your page
Naturally you need to be an administrator of the page you are visiting to be able to remove something.
Step 2 - click on the little down arrow
Step 3 - uninstall app
Click on the pen icon next to the app you want to uninstall. Then select "uninstall" from the menu that comes up. Done!
The steps above make the app invisible on your page. However if you want to make sure that the app also no longer has any privileges to post or make changes, go to your installed apps list on Facebook
, find the app in question, click the X on the right side of it and click "remove".