Instructions
Go to Lavender Town in the east of the Kanto region. Head to the Radio Tower and talk to the Radio Controller.
Head to the Power Plant on Route 10, to the south of the Rock Tunnel. Head inside and talk to the man inside, who will tell you that someone has stolen a part from the machinery.
Go west along Route 9 to Cerulean City, and head into the Pokemon Gym. A Team Rocket Grunt will run away when you come in -- he has hidden the machine part on the left-hand side of the room.
Pick up the machine part and head back to the Power Plant. Give it to the owner and he will restore power to the Radio Tower.
Go back to the Radio Tower in Lavender Town, and talk to the Radio Controller. He will upgrade your radio card.
Head south on Route 12, then west onto Route 11. Go to the end of the Route and find the Snorlax asleep at the entrance to Diglett's Cave.
Open the radio application on your Pokegear. Use the stylus on the bottom screen of your DS to move the tuning button towards the top of the sphere. You will find the "Poke Flute" channel there.
Select the "Poke Flute" radio channel and the Snorlax will wake up and attack you. It is at Level 50 but, as a Normal-type Pokemon, you can beat it easily with Fighting-type attacks.