How do I create a new app for a managed facebook page

I'm not sure what you mean by a managed profile. If you mean a Facebook Page (Business Page, whatever), there's no way to do that. Each application must be created by an actual user, not by a Page. Pages are the same way, they have to be created by an actual user. This is a requirement by Facebook, and there's no way around it. When an application is created though, your profile is not promoted as being the 'owner' of the App though, so it shouldn't be a problem.

If you meant something else, just let us know.

Thanks,
Alex