Things You'll Need
Instructions
With the Mystic Ticket
Gather a strong team of level 70 Pokémon, as you will fight Ho-Oh at level 70. Field a mix of water and electric Pokémon, as well as Pokémon capable of inducing sleep. Bring a hefty supply of Ultra Balls.
Go to Vermillion City and talk to the sailor at the wharf to the south. Choose "Navel Rock" when he asks where you want to go.
Climb the long stairway until you reach a small set of stairs and a forked path. Head left until you reach another stairway, then head up to find Ho-Oh perched atop a rock.
Save your game, as you will only have one shot at catching Ho-Oh otherwise.
Approach Ho-Oh and press "A" to initiate combat.
Bring Ho-Oh's health down to the red and put it to sleep before attempting to use an Ultra Ball. Continue putting Ho-Oh to sleep and using the Ultra Balls until you've captured it.
With Action Replay
Connect the Action Replay to your Game Boy Advance and plug your Pokémon: FireRed cartridge into the Action Replay.
Power on the system and select the "Code Entry" option from the menu.
Enter the master code for Pokémon FireRed, which is "72BC6DFB E9CA5465 A47FB2DC 1AF3CA86."
Enter the code for Ho-Oh, which is "437065EF 67DF37EF."
Start the game and search areas where you'd normally find Pokémon (tall grass, caves, etc). Your first Pokémon encounter should be Ho-Oh. If not, continue searching until you encounter it.
Bring Ho-Oh's health down to the red and put it to sleep before attempting to use an Ultra Ball. Continue putting Ho-Oh to sleep and using the Ultra Balls until you've captured it.