To begin your adventure in Pokémon Colosseum, you'll need a GameCube console and the game disc itself. Ensure your GameCube is properly connected to your television and powered on. Insert the Pokémon Colosseum disc into the console's disc drive. Upon booting up, you'll be presented with the game's title screen. From here, you can select "Start Game" to begin a new adventure or "Continue" if you have a previously saved game. If starting anew, you'll be prompted to choose between "Story Mode" and "Battle Mode." For your first playthrough, selecting "Story Mode" is highly recommended to experience the game's narrative and learn its mechanics.
The game utilizes memory cards for saving your progress. Make sure a compatible GameCube memory card is inserted into the console's memory card slot. The game will automatically save your progress at desated points, but it's always good practice to manually save when prompted or after significant achievements. If you plan to trade Pokémon with other GameCube Pokémon titles like Pokémon XD: Gale of Darkness, ensure you have the necessary Link Cable and a second GameCube console with the compatible game.