...You CAN'T!
you cant. you can only get registeel from Pokemon sapphire, emerald, and ruby.
You can find Regigigas in Snowpoint Temple in Pokemon Diamond, you will need to bring Regice, Registeel and Regirock for Regigigas to waken.
Registeel is unobtainable from Pokemon Diamond and Pearl. You have to migrate it from Pokemon Ruby, Sapphire, or Emerald.
you cant get registeele in Pokemon diamond
Registeel,Regice,and Regirock are all Pokemon your required to migrate from their respective game(s).
You can't find registeel in Pokemon HeartGold.
In order to catch Registeel in Pokemon diamond, you need to have gotten a level 100 Regigias from a mystery event. This mystery event has passed, so you can no longer get Registeel in Pokemon diamond, unless a friend trades you the mystery event Registeel. The only other way to get Registeel is to trade him from Pokemon emerald, ruby, or sapphire.
You can not catch Registeel in these games. You have to catch him and the other regis on Pokemon Emerald, Ruby, or Sapphire and migrate them to Pal park your wrong go to route 228. there you will find it.
No. You can only migrate them from previous Pokemon Game Boy Advance Games.
You must transfer registeel from a GBA game to your diamond/pearl game in order to obtain it.
you can but i don't know how yet
You can't find Registeel in Pokemon Platnium. You just migrate it in Pokemon Ruby, Pokemon Sapphire, and Pokemon Emerald.