Go defeat the 4th? :)
go on the ship found in vermillion city first of all you have to have defeated blaine the cinnibar gym leader
The 8th gym leader is in Viridian City.
The sixth gym leader,Sabrina, is in Saffron City.
If you mean the third gym, then it is located in Mauville City. In which the gym leader is an electric type which can easily be defeated by a ground type pokemon.
The fifth Gym Leader in Pokemon LeafGreen is Koga, the leader of Fuschia City's Gym. He specializes in Poison-type Pokemon and hands out the Soul Badge.
The third gym leader is Whitney.
Viridian City, Giovanni(Team Rocket Leader) is the Gym leader.
Step on the portals until you get to the gym leader.
It depends on what gym you are talking about all of them you can get to by going to the towns.
You get it from the Fuschia Gym leader
Yes.
You go on to defeat the eight gym leader.