how do u get the regi's

There are in different caves/tombs in Pokemon Ruby and Sapphire, and you must have a Relicanth to access them, which is the brown fish that looks really ugly and stuff. Not Feebas, because Relicanth is bigger. I'm not sure if that's how you spell the name of the fish, but if you dive underwater in the sea and search in the seaweed you can find him. He is extremely rare, though.

All I know is that I heard you have to get a relicanth then I heard about the three stones in the desert I didnt know what to do and wandered around then suddenly it opened :0 I was happy I caught regirock

Catch first a wailmer then evolve it into wailord. If you have, catch a relicanth. Now if you have these Pokemon, go to pacifidilog town. Ensure first you have Pokemon knows dive, surf and dig. Then surf until you have encountered a dark patch of water. Dive here. Now if you see a Braille (dots as characters), go here and dive again. You are now in a mysterious cave with mounds of earth. Walk north and you have a braille read, use dig. Instead of escaping, there's a cave open. Now go inside and arrange wailord in first party and relicanth sixth party. Now read the braille again and you will heard something open. It opens island cave for regice on north of dewford city, desert ruins for regirock on sandstorm, and ancient tomb for registeel west of liliycove city. Now if you want to catch regice, stock up balls and all of regis are level 40 and are weak to fighting so blazikien will take apart. Now if you are in island cave, read the braille and walk close to walls clockwise amd it will open. For desert ruins, bring a Pokemon knows rock smash. Then read braille then walk 2 left and 2 down. Then use rock smash. For registeel, bring a Pokemon knows flash. As after read braille, go to middle of cave then use flash. Hope this helps a lot.