This is already fully explained somewhere on this board, but I'm too lazy to find it so I can link to it...just like you were too lazy to dig for it yourself. So I'll just present the info again.
Unlocking the Caves of the Legendary Golems
In the floating town of Pacifidlog, a legend is passed down about "six dots unlocking three doors". There is a sealed cavern hidden somewhere in the rapid currents that run betwen Pacifidlog and Slateport. That cavern holds the key to unlocking the caves in which Regirock, Regice and Registeel lie dormant. You'll need the moves Surf, Dive and Dig, the specific pokémon Wailord and Relicanth, and the ability to translate the six-dot alphabet known as Braille. For that, check out this web page. As far as getting to the sealed chamber, you should start from Pacifidlog and enter the rapids on the south end. Yoiu'll wash up on a crescent-shaped island. Go west from there to a shallow spot shaped like a windmill, with a spot of calm water in the middle. Go west again; you'll be swept around a large dark area surrounded by rocks. Although the dark area looks like you could dive in it, there is no known way to get in there. Keep going west. You'll come to a shallow region filled with rocks and bordered on the north by by a long outcropping. Keep going west.
When you come to a shallow spot that's shaped like a stack of three rectangles, that when you'll have to do more than just "keep going west". You're aiming for a spot where you can use Dive, but it's guarded by current, and the way in is only two squares wide. Standing on the eastern edge of the shallows, go directly south until you can't anymore without surfing. Now, turn west and walk to the west edge. You should be a little south of the middle of this edge. Surf west. Once you're in the dive area, head on down and start looking for Braille. Translate the Braille using the web page I linked to, and follow the instructions.
Regirock
Now that you've used the six dots to unlock three doors, you need to find those doors! Fortunately, they aren't completely lost to civilization. Others have come before you and searched for the caves. There is a trainer in the game called a "Ruin Maniac". You may have met some; one of them, Ruin Maniac Dusty, is a Trainer's Eyes trainer. The fact is, there are exactly three Ruin Maniacs in the game, and they're all exploring the locations of the Legendary Golems!
Ruin Maniac Dusty himself is at the location of the first cave, in the south side of the Sandstorm Desert on Route 111. Toward the southern end is a large rock surrounded by six smaller rocks. Now that you've unlocked the doors, there will be an opening in the large rock! Walk on in.
There's one more puzzle you have to solve, though. The room is empty save for some Braille on the far wall. Translate the Braille and follow the instructions. You'll open the way to Regirock. Now all you have to do is catch it!
Regice
This cave is rather far out of the way. It's in the ocean northwest of Dewford. When you spot the Ruin Maniac, you'll know you're going in the right direction.
As with Regirock, you should find a large stone surrounded by six smaller ones, and the large stone should have an opening in it since you unlocked the doors in the Sealed Chamber. As with Regirock, the room appears to be emptty, but translating some Braille and following the directions will open the way to Regice.
Registeel
Registeel's cave is in the Rainy Forest. More specifically, it's on the north end of a high plateau on Route 120. Again, keep an eye out for the Ruin Maniac to tell you you're in the right place. Enter the large stone, translate the Braille, open the way to Registeel and catch it!