Instructions
Go to Radio Tower in Lavender Town in the east of the Kanto region and head inside to find the Radio Controller.
Speak to the Radio Controller and he will tell you that the power to the tower has been shut off due to a problem at the Power Plant. Go to the Power Plant on Route 10, to the south of the Rock Tunnel, to investigate.
Speak to the man inside the Power Plant to learn that someone has stolen a Machine Part. Leave the Power Plant and head west along Route Nine to Cerulean City.
Enter the Cerulean City Pokemon Gym and a member of Team Rocket will run out. Go to the top left of the pool to find the Machine Part hidden under the rubber rings.
Take the Machine Part back to the Power Plant and give it to the man there to restore power to the Radio Tower.
Go back to the Radio Tower in Lavender Town and speak to the Radio Controller to get your radio card upgraded.
Go south on Route 12 and turn west onto Route 11. Head right to the end of the Route to find a sleeping Snorlax blocking the entrance to Diglett's Cave.
Select the Radio Card application on the touch screen of the DS and use the stylus to move the tuning knob to 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 until it is showing as a red bar and throw a Pokeball to catch it.