1. Turn on your Wii and insert the Just Dance 3 game disc.
2. Open the game and use the Wii Remote to navigate to the "My Music" menu.
3. Select the "Locked" tab at the top of the screen to see the songs that you have not yet unlocked.
4. Find the song "Teenage Dream" and press the "A" button on your Wii Remote.
5. You will be given a challenge to complete in order to unlock the song. The challenge for Teenage Dream is to score a "Perfect" on a specific part of the song.
6. Once you have successfully completed the challenge, you will unlock the song and it will be available to play.
Note: If you are unable to unlock the song by completing the challenge, you can also purchase it through the Just Dance 3 in-game store using Just Dance points. To earn Just Dance points, you can play the game and earn stars, or you can purchase them with real money.