How does the ViewPortFrame GUI object work?

So i want to make a Menu Screen with a character popping by once in a while. I want to make this character as realistic as possible, so i decided to use a ViewPortFrame.

However, i can't get this ViewPortFrame thing to work.

This is how i have it set up: ScreenGui > ViewPortFrame > Model Does anyone know how to fix this? It would be really awesome to use it. Thanks!