Once you've got either the Root or Claw Fossil then you will need to head to the Devon Corporation in Rustboro City and then head to the first floor and talk to the scientist in the extreme bottom east, he will be the one that can resurrect Fossils into Pokémon.
The fossil Pokemon available in Pokemon Emerald include Anorith, revived from the Claw Fossil, and Lileep, revived from the Root Fossil.
Take the fossil to the Devon Corporation in Rustboro City. Go up a floor and talk to the scientist at the bottom right of the room. He'll turn your fossil into a Pokemon.
You get Anorith from a certain Pokemon fossil.
The root fossil must be brought to the Devon Coronation in Rustboro city. The fossil will then be revived into a lileep Pokemon. The claw fossil also found in emerald revives into the Anorith Pokemon.
You can turn in your fossil in the Nacrene museum. Speak to the lady on the right. There, the lady will change the fossil to a pokemon!
kabuto and omntye. kabuto is the left fossil and omantye is the right fossil.
He's at Fallarbor Town
In the desert and in mirage tower.
when your in the cave where you get ditto (in fossil manics house) go in the cave after you beat the elite 4 then go all the way right
The Helix Fossil, as well as the Dome Fossil, do not appear in Pokemon Emerald, Ruby, or Sapphire. The only two fossils obtainable in Emerald are the Root and Claw Fossil, which can be found in the desert in Route 111 (for Emerald, they are at the top of the Mirage Tower which appears and disappears frequently in the Desert), and you can only pick one of the two.
Claw Fossil - Anorith Root Fossil - Lileep
The Dome Fossil can be revived into the pokemon kabuto.