Things You'll Need
Instructions
Insert the GameShark into the Game Boy Advance Cartridge.
When prompted to add a cheat code, insert the Fire Red cheat code: 17543C48 E65E0B97. Then insert Ho-Oh's cheat code: 437065EF 67DF37EF. Save this, then restart the Game Boy Advance. Insert "Pokemon Fire Red."
Go out to the grass. The first Pokemon that you're going to battle is going to be Ho-Oh. Weaken it and use a Pokeball to capture it.