You don't. You use the radio on certain days of the week. Dj ben says"lets wake up ypu pokemon with a march" or somthing like that
Where Do You Get The Poke Flute To Wake Up The Snorlax In Soul Silver?
It is a app on the pokegear. First go to lavander city and go to the radio stationm then there is an old guy, he talk about a power plant that is not working. Go upto route 10 then get on the river and surf down. Then a team rocket will get out and go to the cerulean city and hid it on the last tube. Go back and give it to the man in charge of the power plant. He will give you a tm and then go to lavander city and go to the radio tower. He will give you the poke flute app and wake up the snorlax and he is at lvl. 50! HOPE IT HELPED!!!! :)
It's there in your poke-gear once you tune it to the poke-flute channel. .