After you make your way through Route 23 following the battle in Giant Chasm, you finally reach Victory Road.
Badge Check Gate
When you enter Victory Road, N is there waiting for you. He tells you more about what he has learned, then gives you HM05 Waterfall so you can access all of the areas of Victory Road. Then N leaves for Route 23.
Go west to walk through the badge checkpoints, then go north up the stairs to the gate, which opens for you. To the north, there is a Pokémon Center.
Turn on your Dowsing Machine to find a Dusk Stone in the maze-like ruins to the east.
Go south from there to get the PP Up that you can see out in the open. Then go as far southeast as you can go, and start going north along the right side of the ruins until you reach the Star Piece up above.
Drop down the ledge west of where you got the Star Piece and use your Dowsing Machine to find an Iron to the south.
Go north to the Pokémon Center, then walk east. There is a secret path to the east that leads you to TM01 Hone Claws.
Visit the Pokémon Center if you wish.
To reach the Pokémon League, you need to bring a pokémon that knows Strength. If you want to visit all of the areas of Victory Road, you need pokémon that know Strength, Surf, Waterfall, Flash, and Cut.
When you're ready, go west from the Victory Road pokémon center and then north. There are some stairs down into a cave. Use those stairs to enter the Victory Road Ruins.