Go to snowpoint city after beating the Pokemon league and speak to the sailor next to the boat and he asks you if you want to go to the battle zone and then he takes you there but to get further you have to complete the sinnoh pokedex by seeing every Pokemon in sinnoh and then the people blocking route 225 and 230.
It takes time but figure it out.... push the boulders
Beat the Pokemon league
Unfortunately the only area for good training is the Pokemon league.
you beat the pokemon league and if youre talking about the one on victory road you have to get the national pokedex
U hav 2 Dfeat the pkmn league
must obtain the required number of league badges
skill
You have to beat the league.
Get 8 badges
beat the Pokemon league
Ghost, Fire, Ground, Psychic, and Ice
Go to sunyshore city, then go up in the water (make sure you got surf and waterfall) to swim and to go up the waterfall to The Pokemon League then you will reach a Pokemon league cave past it and then go to the Pokemon league heal your Pokemon and fight
At the fight area (after you beat the Pokemon league)
route 2 in the island you open after getting past the Pokemon league
You can use any Pokemon. As far as I know you don't have to use certain Pokemon to challange them.
In the Pokemon League in Yellow, the strongest Pokemon Lance has is a Dragonite. When you get past him, still there's Gary that finished the league before you do. His stongest Pokemon is Jolteon, an evolve of Eevee. It is level 64 and it is really strong.
You get in on the giant island with the survival area after beating the Pokemon league.