It depends on what you've already done but make sure you beat Sabrina, the Gym Leader there first. If you went to Fuchsia City already and beat Koga, the Gym Lleader there and you already got the HMs of Surf from within the Safari Zone and the HM of Strength by retrieving the Warden's teeth and giving them to him so you get the HM of Strength and you can now go to Cinnabar Island. You can either go get there by Surfing on the water south of Fuchsia City and head west or you could Fly to Pallet Town and Surf all the way south until you get to Cinnabar Island. Next you go into the Pokémon Mansion to find the key to the Cinnabar Gym.
Use the Silph Scope. You get this by defeating Team Rocket, when they steal it.
Go to Viridian city and beat Giovanni,the gym leader
You have to win the Silph Scope (c) from Giovanni, the Team Rocket Headmaster.. He is located in Saffron City's Game Gallerym in their secret hideout
go on an elevator
on the second floor
You can get a Master Ball at Silph Co. from the Silph Co. President after you beat Giovanni.
Use the Silph Scope. You get this by defeating Team Rocket, when they steal it.
First you must defeat him at the game corner and silph co then you must get 7 badges now Giovanni should be at the gym.
From Steven Stone in Silph Building after defeating Red on Mt. Silver
you only get one as a gift for silph co. for defeating team rocket
Go to Viridian city and beat Giovanni,the gym leader
Steven will appear in Silph Co. after you defeat Red at the top of Mt. Silver. He will be there to give you the Hoenn starter Pokemon. He will not be there before defeating Red.
He is the boss of team rocket, after defeating him at the game corner and silph co he will return to his gym in viridian city where you can challenge him for the last badge.
You have to win the Silph Scope (c) from Giovanni, the Team Rocket Headmaster.. He is located in Saffron City's Game Gallerym in their secret hideout
After defeating Red at Mt. Silver, Steven Stone will be at the Silph. Co and he will give you one there.
the 6th gym is in saffron city if that's the city you are talking about then to unlock the gym you have to defeat Giovanni in Silph co. if there is a team rocket player there BLOCKING THE WAY IN then you got to beat Giovanni in the basement of the game corner (team rocket hide out) to unlock Silph co and then beat him in Silph co. i hope it works in fire red bcos it works in my leaf green
safron city