Press the A key for... well, the A button.
Based off of this video: https://www.youtube.com/watch?v=f3GO2ILfMKA Original description: This Wii prototype had more of a green color scheme. The UI is similar to the finished UI, but slightly off. This might have been recorded before the infrared technology was completed, because no cursor is visible. Instead, it appears to be selection based. This footage appears to be in Japanese. This is a work of fiction.