You go to where the girl (Jasmine) is under the Gym on the beach and she will give you Waterfall (the HM obviously. You surf on the water behind her and when you get to the waterfall use waterfall, then go through Victory Road, and Then face the Pokemon League.
the seventh gym badge snowpoint gym
The 8th gym is in Sunyshore, but you will be unable to go there until after you beat Cyrus on Mt. Coronet.
beat the league
In Diamond, Badge 5 can be gotten by defeating Fantina in her Gym in Hearthome City.
get the 4th gym badge and then give him a pokemon... get the 4th gym badge and then give him a pokemon...
you beat the gym leader
Sunnyshore City Gym: Electric (beacon badge from Volkner)
the seventh gym badge snowpoint gym
you will get it from the girl at the 8th badge gym she will give you the hm 07 waterfall
Hearthome
The 8th gym is in Sunyshore, but you will be unable to go there until after you beat Cyrus on Mt. Coronet.
you beat everyone in the gym
beat the league
snowpoint city
beat the #?*@! gym leader
In Diamond, Badge 5 can be gotten by defeating Fantina in her Gym in Hearthome City.
By beating the gym leader