Now copy/paste the following url into the text document:
http://facebook.com/add.php?api_key=[YOUR_APP_KEY]&pages=1&page=[YOUR_PAGE_ID]
Then replace the [YOUR_APP_KEY] with App Id and [YOU_PAGE_ID] with the Page Id value.
From my example like this:
http://facebook.com/add.php?api_key=162756690570780&pages=1&page=251744304905768
Now copy/paste the complete url to your web browser and simply click the Add button. If everything went well, your Facebook app should now be visible on the Facebook page you were adding it to.
If you get lost in the process, please don't hesitate and drop me a comment.