Instructions
Load the game. Wait for the title screen to appear.
Select the "Load Game" option.
Select the "Passwords" option on the load game screen.
Type "89631139" into the password entry box. This action unlocks "Blue Eyes White Dragon" in the shop. Now you can use the card in your decks.
Defeat the "Meadow Mage" in dueling mode. He drops "Blue Eyes White Dragon," among other rare cards, when you beat him.
Defeat "Labyrinth Mage" in dueling mode. He also drops "Blue Eyes White Dragon."