How do you past Snorlax in Pokemon LeafGreen?

After defeating Team Rocket in Lavender Town Pokemon Tower, you will be taken to Mr. Fuji's house. There he will give you the poke flute, which can be played to wake Snorlax up. When awoken it will battle you; be prepared, Snorlax is a powerful pokemon and you don't want to miss your chance to catch it.

From there it's a simple matter of catching or defeating Snorlax to move past him in the game.