Things You'll Need
Instructions
Connect the two Game Boy Advance systems via the Game Link Cable.
Have each member of the trade (or, if you're transferring from one of your games to the other, each player character) go to a Pokémon Center in any town.
Have both trade members head upstairs and speak to the Cable Club Trade Center representative to initiate the trade.
Select a Pokémon to trade for Raikou, Entei or Suicune. When simply trading from one of your own games to another, any Pokémon will do. However, if trading with another player you may have to specifically negotiate a Pokémon to trade in exchange for one of the Legendary Beasts. As rare Pokémon, they are more valuable than average Pokémon.
Complete the trade and exchange Pokémon. When finished, you will have one of the Legendary Beasts available to you on your Ruby version game. To gain the other two, you will have to perform further trades.