Have fun. This is a fun feature.
One: Turn the black wheel on top of your camera to the video camera icon.
Two: Press the blue "Function Setting" button at the center of the black button to the right of the window.
Three: Move the orange pane onto the miniature icon.
Four: Press "Function Setting," and you're good to go.
This is my initial attempt:
The miniature effect works a lot better if you're shooting down on subjects from an upstairs 2-story building.