Beat the rest of the gym leaders first.
You must go and battle Misty. Once you defeat her, she will give you a badge. You have then defeated the gym.
you need to first go to the power plant and find out that there was a thief and then find him in Misty's gym and then interrupt misty's date on route 25
USE YOUR MAP and it is near the water gym(gym leader misty)
I don't have heart gold but its Vermilloin city next gym leader is Lt.Surge he has electric Pokemon No,Brock is next,ok?
it is not in the water, you go to the top left corner and press a while facing the inner tubes
To get to misty you beat all the gym leaders johto then the person who gave you your first Pokemon will give you a ticket to go to kanto. You will be in vermillion city. There will be a problem with the power plant found by surfing. Once you fix that problem you can find misty by the cape then you can face her in a gym battle. Yeah!
Go to the Gym talk to Misty than go to the pokemon league and go back to Misty
go to the gym and talk to the guy
you go to azalea town
Go to the forth gym!
go to the next gym leader.
go to the third gym (lt.surge)