Facebook: You must have permission to add apps to at least one Facebook Page to perform the requested action

nope, that answer is not helpful. There is an error message following your instructions that says, and quote "You must have permission to add apps to at least one Facebook Page to perform the requested action."

This is a Facebook error that you see when you don't have permissions to add apps to a specific page . Here's an existing community discussion pointing to the exact message you're getting:

https://www.facebook.com/help/community/question/?id=10151686924230743

A user claims he managed to make it to work by:

Going to settings on your FACEBOOK PAGE, then page roles, then enter your name or email as an editor. NOW Make sure you log into your PERSONAL PAGE to ad apps to your FACEBOOK PAGE 

In case you need more help, don't hesitate to let us know.