Go to Kanto, and go to the town where Brock's gym is. Right north of his gym is a bug museum like house. Go inside, talk to the geek to the far east of the building, he'll take ONE fossil at a time. Go outside and come back in and talk to him. Make sure you have a space in your party, and you have that fossil pokemon.
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after you defeat ash, it is found in Johto, there you can find it
you cant
in the museum talk to the guy alone at the desk he will revive it
You use rock smash and can sometimes find fossils.
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.