Instructions
Power up your Nintendo Game Boy Advance or Nintendo Game Boy Advance SP and insert the "Pokémon Emerald" game into the cartridge slot.
Complete the Elite Four mission and then walk to the bottom level of your "Pokémon Emerald" house. Walk to the television set found in your house and choose to accept and reveal Latios.
Go to the "Mix Records" section to connect with a friend who owns "Pokémon Ruby" or "Sapphire" and has an unlocked Eon Ticket. This is necessary to gain access to Southern Island, where you will find Latios.
Save your game data to be able to access Latios every time you play "Pokémon Emerald."