You don't, you can only catch Rayquaza in Emerald, Groundon in Ruby, and Kyogre in Saphire.
STUPID ANSWER !!!!
YOU CAN beat elite four then go to weather institute then he will tell you there is a drought on route ___ and a heavy rainfall on route___ go to that route and you will find groudon in terra cave and kyogre on marine cave rayquaza is in sky pillar.... groudon,kyogre and rayquaza are all level 70 for groudon you need at least 30 ultra balls and kyogre 40 ultraballs and for rayquaza, the toughest you can use the master ball that can be found in team aqua's hideout.
THE ONE AT THE TOP IS WRONG THE ONE WHO ANSWERED IT IS NOT A MASTER this is jessonmudkip**** ENJOY!!!!!!!
Chat with our AI personalities
you can not get Growdon on heartgold but Ruby and the 2 games that go with it you get at a cave in the city that has the 8th gym leder
You can't find a Dawnstone in Pokemon Emerald
he is the champion in emerald
You can´t find it on Emerald
you cant get reggiggas in Pokemon emerald