1. Power on your Nintendo DS and insert the HeartGold game cartridge.
2. On the title screen, you'll see a few options:
* New Game: This is the option to start a fresh game.
* Continue: This is to load a saved game.
* Options: This lets you adjust game settings.
3. Select "New Game". You'll be prompted to enter your name and choose your gender.
4. Choose your starter Pokémon: You can pick between Cyndaquil (Fire), Totodile (Water), or Chikorita (Grass).
5. Begin your adventure! You'll start in your bedroom in New Bark Town and be guided through the initial tutorial.
Important Note: If you've played HeartGold before and have a save file, make sure you save your existing game progress before starting a new game. You can choose to overwrite your old save file, but if you want to keep your progress, you'll need to create a new save slot.