Here's how it worked in those games:
1. Catching a Snorlax: The Poké Flute was the ONLY way to wake up a sleeping Snorlax.
2. Location: You could only obtain it after defeating the Elite Four and becoming the Pokémon Champion.
3. Use: Use the Poké Flute in battle against a Snorlax to wake it up and allow you to fight it.
Important Notes:
* Not in later games: The Poké Flute is not a standard item in later games. Snorlax can be woken up by other methods, like using a Poké Ball or a move like Wake-Up Slap.
* Special cases: There may be specific situations in later games where a Poké Flute is used as a plot device, but it won't be a general item.
If you're playing a different Pokémon game, don't expect to find a Poké Flute!