You have to beat the Gym Leader in Mahogany town and then beat Jasmine (Olivine/Steel Gym), and Chuck(Cianwood/Fighting Gym)then you need to go to the lake of rage and catch SHINY RED GYARADOS and then you can get past the guy who sells RageCandyBars...
you have to get rid of team rocket in goldenrod city, but first you need the gym badge from mohogany. When you do this, you will be able to pass to get to blackthorn
in mohogany town where the seventh gym is at
You can't get to it in soulsilver.
olivian town
Next to mohogany town if you go right and you surf to the middle of the water you will find wild lickitung.
Between Mahogany Town and Lake of Rage.
it's right after cherrygrove town
you get it in pewter town
in pallet town.
The Kanto radio station in both Pokemon heartgold and soulsilver is in Lavender Town.
red gyarados is nowhere you need to find a shiny magickarp then train it to a level 20. For SoulSilver/ heartgold Version: The red gyrados is in the lake of rage. Go north from Mohogany Town ( IN Johto) make sure that you bring the Pokemon that knows HM surf.
in pallet town (above cinnabar island)