On any stage after you complete a song, you will have the option to make a music video. Select that option. You then may get the option to edit with effects. One symbol has pair of 3-D glasses. Select them and continue editing your song. When you watch the song after you are done editing the part with the 3-D glasses, it will have the symbol of the glasses in the corner of the screen. If you pause the music video there and put on real 3-D glasses, that scene will appear in 3-D.