Take your fossils to the Oreburgh City Mining Museum, which is just North of the PokeCenter. Walk to the back of the building and talk to the scientist guy behind the counter. Then just walk out of the building and walk right back in. Your fossil will be revived. Make sure you have an open slot in your party, otherwise you can't atke the Pokemon.
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You could revive it at the oburgh museam
in the museum talk to the guy alone at the desk he will revive it
You can revive fossils in Pokémon White in the museum in Nacrene City. Once you have entered the museum, talk to the person in the blue hat on the right hand side.
level 20, as with all fossils in all games
You turn in your fossils to the scientist inside the museum of Oreburgh City.