With a special password you find somewhere in the game
In the game corner
He Whent to The Rocket Hideout on Five Island.
You can get in the rocket hideout Which is in the five isle meadow. You can also get it when participating at the trainers tower. (do single mode battle.)
If you are talking about the Pokemon Tower, then first, you need the Silph Scope, which you can obtain by beating Giovanni in the Rocket Hideout at Celadon City, in the Game Corner.
Floor 1, 2 and 4.
In the game corner
You must beat team rocket at Pokemon tower and the rocket hideout then get the 5th badge.
After beating the boss at the Rocket Hideout in the Celadon Game Corner.
you get in the team rocket hideout on one of the islands
Team rocket will go to the dotted hole after five island in leafgreen, but I'm not sure about firered.
To open the rocket hideout, you need to get 2 codes. Lorelei will give you the 1st code in Icefall Cave. Then you go to Island 6 and go into the ruins. You will find a scientist who will tell you the 2nd code. Now go to the rocket hideout on Island 5 and beat up those miserable rockets.
you go to six island, go to dotted hole, and use cut at the door. it will open. when you find the crystal, someone will steal it and go to the rocket hideout. it will be there.
He's first at the team rocket hideout in celadon city, then silph co, then the viridian city gym.
You can use it to operate the elevator in the rocket hideout, under the casino in celadon city. Hope this helped you!
He Whent to The Rocket Hideout on Five Island.
Mt. Moon, Pokemon Tower, Rocket Hideout, Silph Co., Fuchsia City, Victory Road, and Lost Cave.
The gem is on Six Island east of the Pokémon center in long maze. At the end of the maze someone will still it and tell you the password to Team Rocket's hideout on Island 5.