You cannot. You will have to trade it.
you need REGIROCK, REGICE, AND REGISTEEL.
train them
to catch regirock u go 6 down 9 left and 39 up
Regirock, and finally Registeel.
no you can, you most catch it in Pokemon emerald
Sorry but you have to catch Regice, Registeel and Regirock in order to catch Regigigas.
You can only get a regice, regirock, and a registeel by migrating them from ruby or Sapphire. If you migrtate these Pokemon you can also catch regigigas.
you cant. regice regirock and registeel are all part of the hoen pokedex
he is at the bottom of the Snow Temple. you will need to have regice, registeel and regirock with you to awaken him.
you must catch regice,regirock, and registeel
NO. you can only catch deoxys if you have an event or if you are a cheater.
get lv.100 regigigas through wi-fi event and carry it with you to iron island (registeel) mt. Coronet (regice) and the cave on route 228 (regirock)