Instructions
Plug the wireless adapter into the top of your Game Boy Advance. If you are using a Game Boy Advance, the label should be facing you; if you are using a Game Boy Advance SP, the label should face away from you.
Insert "Pokémon FireRed" into the game slot on the Game Boy Advance, and turn on the system.
Start your game and travel to a Pokémon Center. Go to the second floor of the Center.
Talk to the woman on the far right of the room. This is known as the "Direct Corner."
Select "Colosseum" and choose your battle style from the options. If you are playing a multiplayer battle, choose the side you want to play on and pick the Pokémon that you want to use.
Choose "Trade Center" to trade Pokémon with your friends. Browse your friend's Pokémon and select which ones you want to trade. If you both agree with the terms, approve the trade.
Visit the Union Room by speaking to the woman in the middle of the room and selecting "Union Room" from the dialog box. The Union Room can hold up to 39 players with whom you can chat, battle or trade.