You need to have downloaded it from the Mystery Gift online event that already ended so now, you need to use an Action Replay with the correct code.
You can get it through the Nintendo wifi.
first you must have 666666666666 darkrais than you can talk to the man in ##### and jubilife town than you get the members card
you have to obtain the members card through mystery gift.(it may be possible trough AR.)
the event passed so u need action replay
With the Japanese event or mystery gift
You can get the member card in diamond and pearl but the event for it in platinum is august 3rd to September 13th (you have to have wi-fi connection to do this)
you get it through Nintendo event or mystery gift on Pokemon pearl platinum or diamond
go to canalave, walk up to the harbor inn and sleep... hope i helped
Members card. Go to the inn in the city where you go to iron island that was before locked. There you go.
you need to wait for the event which will come out hopefully in June they said whrn the arcues movie comes out
it wont do any good like you can only use it to get darkri in platinum or pearl
the master card is not an item in Pokemon diamond and pearl. you may mean the members card? this allows you to get into the hotel in (getting into the hotel starts off the darkrai saga) when you get inside the hotel you are put into a bed and have a dream about darkrai and then when you leave the hotel go to the sailor that took you to full moon island. he will be able to take you to darkrai and when you battle him he is level 45 so save beforehand and be careful. now to get the members card you shall need to go to the pokemart in canalave and speek to a man in blue near the counter he will give you the members card.