Where do I find kyogre and groudon?

Go to the Weather Institute. Talk to the man that gave you the Castform. He'll tell you there have been droughts (for Groudon) or drizzles (for Kyogre) in certain places. Go to those places a look for a while, and eventually you'll find the lair of either Kyogre or Groudon.

You have to go to the weather station on route 119(i think) and he will tell you where it has been raining alot (kyogre) then after you chatch or defeat kyogre he will tell you where it's been very sunny thats where you chatch groudon.
Assuming you've beeten the E-4(must do that first)

Well first you need to have beat the elite 4 then go to the weather institute on route 119 talk to the scientist he will say there is a drought on either route 114 - 116 or 118 were you will find Terra cave were you can find groudon (hint Terra cave allways appears on a rocky mountain side or cliff face), or he will say massive downpoor on either route 105 - 125 or 127 were you will find Marine cave were kyogre is ( you will need HM03 (surf) and HM08 (dive) to get into Marine cave). If you take to long tring to find the cave then it will dissapear and go somewere else. Groudon and Kyogre are both lv70 so be careful and take lots of ultra balls.

Once you've defeated the Pok�mon League, go to the Scientist on the second floor of the Weather Institute. He'll tell you that heavy rains are on either Route 105, 125, 127, or 129. Go to the route he specifies and locate a dive spot that wasn't there before before the rains let up. Go down and you'll find Kyogre.

Once that's done, return to the Scientist and he'll tell you that either Route 116, 118, 114, or 115 is experiencing a drought. Go to the said route and locate a cave that wasn't there before before the sun fades, in which you'll find Groudon.

Try the place you went when you catched Groudon in Pokemon Ruby

Alright, first of all, beat the E4. Then, if you plan on catching both of them, buy a bunch of ultra balls and/or timer balls. And then go to the weather institute (route 119) and talk to the same professor who gave you the castform. Talk to him and he'll mention a drought on 1 of 4 land routes. Go to that route and look for a cave that wasn't originally there. That's the cave where groudon is. Save before you fight groudon, but be sure you're in the cave. Fight, catch, defeat [whatever you want] groudon. Then go back to the weather insitute, and talk to the same professor, and this time he'll mention a rain storm on 1 of 4 sea routes. *Sigh* Go to that route (be sure to have a Pokemon that knows surf and dive) and look for a diving spot that wasn't originally there. Use dive and enter the cave. Save. Move onward to fight/catch/defeat [again, whatever you want] kyogre. And once you've done that, well, you're all done.

First beat the Elite 4, then talk to the guy at the weather inst. He will say something is wrong with the weather at a specific location. Check your map to see where the route is then go there. Make sure you are prepared because unlike ruby and sapphire, kyogre and groudon are on lvl. 70 instead of lvl. 40