To get your Mega Stones:
Select Mystery Gift on the main menu.
Select Receive Gift.
Select Get with Code/Password, then Yes, and then Yes again to connect to the Internet.
Enter your password.
Watch as you receive the Mega Stones.
Speak to the delivery person in any Pokémon Center to pick up your Mega Stones.
Be sure to save your game!
MATSUBUSA - Sceptile, Blaziken, Swampert, Camerupt, Bannette
M2DESCENT - Mewtwo
AZUL - Steelix, Heracross, Pidgeot, Houndoom
INTIMIDATE - Audino, Beedrill, Mawile, Medicham
SABLEVOLANT - Tyranitar, Abomasnow, Manectric, Aggron
POYONG - Gardevoir, Gallade, Lopunny, Diancie
DRACHE - Ampharos, Altaria, Latios, Latias