Instructions
Go to Lavender Town in the east of the Kanto region and head into the radio tower.
Speak to the Radio Director inside and he will tell you that the tower currently has no power due to a problem at the Power Plant.
Head to the Power Plant on Route 10 to the south of the Rock Tunnel, using a Pokemon's Surf move to get across the water to plant. Go inside and a man will tell you that someone has stolen an important Machine Part.
Head east on Route 9 to Cerulean City and go into the Pokemon Gym. A member of Team Rocket will run out as soon as you enter.
Go to the top left of the swimming pool in the Gym to find the Machine Part under some rubber rings. Take it back to the Power Plant to restore power to the radio tower.
Head back to the radio tower in Lavender Town and speak to the Radio Director again. He will upgrade your Radio Card so that you can receive the Poke Flute channel.
Go south on Route 12 and turn west onto Route 11. Go to the end of the road to find Snorlax blocking the entrance to the cave.
Open your Pokegear radio on the bottom screen of the DS and use the stylus to move the tuning knob towards the top of the sphere. Find the Poke Flute channel and the Snorlax will wake up and attack you.
Use Fighting-type moves to wear down the Snorlax's health points until they are showing as a red bar, and throw a Pokeball to catch it.