you can't it's impossible.
You CAN NOT become a Gym Leader in Pokemon HeartGold and SoulSilver or ANY MAIN SERIES POKEMON GAME.
Not enough info: which gym leader?
In the goldenrod gym.
Nope i dont think that would ever be possible lol
beat gym leader
Brock.
defeat gym leader.
in seafoam island
Jeff Gordon
in blackthorn city
He is the Gym Leader in Cinawood.
Simply beat the gym leader in every gym.