Yep, it is pretty confusing but first you must visit lake valor lakefront right after the water gym. You will see Champion Cynthia,(You don't really battle her because you're too weak.)talk to her and then receive the necklace(or the bracelet,i forgot)and the secret potion and if you are playing pearl you will find alot of bonslys go to celestic town and then talk to the lady next to the water, by the pokecenter. Battle the grunt at the ruins or mess with him and go in. Now read the picture. The old lady will be in now and ta da! The Hm surf and access to Fantina!!!!
You can find her at the Contest Hall.
After you get the HM and earn the Fantina in the Hearthome City Gym
In the Hospital. Because she has diarhea.
Hearthome City has the 5th Gym Leader. The 5th leader is Fantina and she uses Ghost-type Pokémon.
She goes to stark moutain to battle razqayza arceus
mom
Beat the forth gym (fighting).
You can find her at the Contest Hall.
canalave
Go to Jubilife city. Then go through the left gate and surf to canalave city. Then beat the gym and continue your game.
Beat maylene and wake first.
in platinum she is in the Pokemon contest center
After you get the HM and earn the Fantina in the Hearthome City Gym
In Diamond, Badge 5 can be gotten by defeating Fantina in her Gym in Hearthome City.
Beat Fantina in Hearthome City.
In the Hospital. Because she has diarhea.
You have to keep traveling in the game, just go dowon route 210 and earn hm03 cause she shows up later to battle with you. She will find you later in the game