Pokémon League is a large group that organizes Pokémon competitions for Pokémon coaches. There are 9 regional leagues that make up the Pokémon League. Be careful, you need all eight gym badges to enter the Pokémon League.
How To Get To Pokémon League – Pokémon Brilliant Diamond & Shining Pearl
When you collect the last gym badge go to Sunny Shore market and just go north of it.
You need to arrive at the beach where Jasmine will be waiting for you. Talk to her and she will give you TM Waterfall.
You will need this later to enter the Pokemon League. Then start surfing north of the beach, you need to find the waterfall, but the road a bit is confusing.
Surfing further you will have to fight with several trainers to reach the waterfall. The next thing you need to do is climb to the top and cross the victory path. Move up and then right and then up and climb the bridge.
Next down the right side of the bridge down. Then move west until you reach the last stairs that lead you up.
Here you will have to fight with the coach and then continue west on the stairs, when you climb the stairs you will need a stone breaker and push the stones.
Here you will have to beat the coaches who will be on your way and then just go down the stairs on the right. Get off the bridge and find the karate coach.
Next, you have two descents and you have to find the water and go north along the water, find the waterfall and go west and south until you find the stairs.
Go west again and then south to the old coach.
Then you will have to climb the rocks to the north and continue along the bridge and here you will find the way out.
Climb to the top of the waterfall and here you will find the Pokémon League.