in order to find them, u have to beat the Elite Four.once u do that, go to the weather instatute and talk to the guy on the second floor. he'll tell u theres a major drough or rainfall. if drough, look for a cave for Groudon. if rainfall, look underwater for a cave with Kyogre.make sure u save before u battle them, so just in case they faint, u can battle them over.
hope i helped!
yea ok thanks alot i really aprechiate ur help