Firstly, have to defeat the 7th gym leader. Then you go talk to the trainer next to the Pokemon center on Cinnabar Island. He is the 8th gym leader of Kanto, Gary. Gary is in Viridian City.
In the goldenrod gym.
You CAN NOT become a Gym Leader in Pokemon HeartGold and SoulSilver or ANY MAIN SERIES POKEMON GAME.
Cinnabar Island.
He is not a gym leader. He is the strongest CPU Pokemon trainer in the Pokemon story. Climb to the top of mount silver and he will fight you.
Not enough info: which gym leader?
beat gym leader
Brock.
u need to push the snowballs around and find a path to her like to pryce the seventh gym leader in pokemon soulsilver and heartgold
In the original Silver game, the gym leader was Blue and you would find him at Cinnabar island. After meeting him there, you can go back to the gym and fight him.
in eutreaka city with the fourth gym leader morty, go to the pokemon center and he should be there
defeat gym leader.
in seafoam island