Ok so first of all you need a 12th movie Arceus (the real deals name is in Japanese)
And I think you need to beat the Elite Four/Red
1st.Ok all you gotta do for the first step is put Arceus in the front slot of your party
2nd.Next step is to head on down to the Ruins of Alphi
3rd.Then look around for Cynthia(if you dont know who she is, she looks like she has a feather in her hair)
4th.Talk to her and then she will bring ya to some different ruins
5th.Go in,and Cynthia will be talking for a bit, and walla
YOU JUST ONE THE LUCKY PRIZE MISTER/MISSES!
A CHOICE BETWEEN PALKIA,DIALGA, OR GIRATINA, ALL LEVEL ONE!
NOW YOU CAN GET TWO GIRATINAS,PALKIAS, OR DIALGAS, BY TRADING THROUGH WI-FI!