How do you get through the rocket hideout?

You go up to the Team Rocket hideout door, and you get a Pokemon that knows cut. Then use cut ( its not going to ask you if you want to use cut or not. You just have to do it on your own) The door will open and you will be able to enter.

Which Rocket Base do you mean?

I am putting down 2.

First: Game Corner Rocket Base.
1. Go to the third floor.
2. Go through the maze (try and work it out)
3. Go to the forth floor.
4. Head to the north-west corner an fight the trainer to get the card key.
5 . Go to the second floor.
6. Go through the maze.
7. Enter the elevator and go to the forth floor.
8. Defeat the two rockets to get to Giovanni.
9. Defeat Giovanni to get the Silph Scope.
Giovanni's pokemon are: Onix LV25, Rhyorn LV24, Kangaskhan LV 29.

Second: Silph Co. Rocket base.
1.Take the elevator to the 5th floor.
2.Go past the first trainer.
3. Go south and fight the trainer near the teleporter.
4. Stand on the teleporter then, when you have gone up, enter it again.
5. Head east and get the item (card key)
6. Go to the 3rd floor and fight the trainer.
7. Using the card key, open the first door on your left.
8. Step on the first teleporter.
9. When you go up in the teleporter, you will fight your rival.
10. Get the Lapras from the worker near your rival.
11. Step on the teleporter, fight the rocket on the 11 floor then fight Giovanni.
12. When you win, collect the Master Ball from the Silph Co. President.
Giovanni's pokemon are: Nidorino LV37, Rhyhorn LV37, Kangaskhan LV35 and Nidoqueen LV41

Hope I helped.