How do I sandbox my .app for the Mac App Store?

How do I sandbox my existing Unity app for the Mac App Store?

I´ve read this article in the Unityforum(Please look at post 3 and 4, the only one I found, also unityAnswers has nothing)about .app sandboxing. But when I understand right this is not sandboxing my app, it just make sure Apple think it is an sandboxed app.
My App iss already at the Mac App Store, but an update for it was rejected because of missing sandbox support.

Same problem here!! How to sandbox an app ?

please help … i need to sandbox my game on unity please !!! 2 month with the same problem. !
thanks