Welcome to C2
One of the ways to achieve what you want is to add a new layer (game over layer) and set the layers initial visibility to invisible (you will find visibility option in the layer properties window).
You can then place all of your game over elements (screen, reset or quit buttons etc.) on that layer.
Then set up an event to make that layer visible once your game over event occurs (e.g. when your ghost collides with the player).
Hope that helps :)