Gear VR back button and exit

I'm developing for Gear VR. There's a line in Oculus performance rules that says "When the user presses the back button, the app must either go back one level in your UI or display a menu with an option to quit the app." How can I make that work with VR standard assets camera prefab? I've tried to add OVR Platform menu script to the main camera but it doesn't work.Thanks!