edit: doesnt seem to work when you copy and paste from this forum some reason,
just go to
http://www.ziuo.net/achievements/
and fill in the form
/run SendChatMessage("yay \124cffffff00\124Hachievement:6524:"..strsub(UnitGUID("player"),3)..":1:9:5:12:4 294967295:4294967295:4294967295:4294967295\124h[Realm First! Level 90]\124h\124r!","CHANNEL",nil,GetChannelName("Trade - City"));