Instructions
Select one of the five main character to play through the main three levels of "Yu-Gi-Oh! Tag Force" with and start that game.
Save your game after every level you complete of "Yu-Gi-Oh! Tag Force." Once you beat the game, select your old save data and click "New Game" to start a new game, so the old save data will carry over the win from the last time you played. Select a different main character to beat the game with on this play through. Repeat the process until you've beat the game with all five main characters using the same save data.
Open a new game on the save data with the five different players saved on it. The Skillful Spellcaster deck will now be in your card decks.