You have to beat(or Catch) Dialga first.
you beat the gym leader
go to lighthouse (top) talk to gym leader
from that gym leader on the beach of sunyshore city (must have beaten the 8th gym)
go to lighthouse and talk to man in binnoculars that is the gym leader
in the grass in the last city the 8th gym leader
In the lower right side of Sunnyshore city
Wallace is the 8th gym leader PEOPLE!!!!!!!!!!!
Volkner is the Gym Leader of the 8th gym.
The 8th gym leader is in Sunyshore City not out of town, he's just up in the beacon lighthouse.(at the top)looking through binculars. this is for Pokemon diamond and pearl!
First you need the sunyshore gym badge then talk to jasmine a gym leader in johto she should give you waterfall you will need it then go through a sea of battling trainers then go through victory road then us waterfall and then you are at the Pokemon league.
8th gym leader
The 6 gym leader in at Canalave City. the gym after the hearthome City gym!!!!!