Where do you turn a fossil into a Pokemon in diamond?

Question

I have a skull fossil but I have no idea were to turn it into a Pokemon.

Answer 1

Go to Oreburg Mueseum and talk to the guy behind the counter.

Bulbapedia

Answer 2

You go to a building behind the Pokemon center
This is Orbeurgh Museum. Talk to the guy on the right of the counter and he will jabble on about fossils-give him the Skull Fossil.
After you do step out the museum and come back and talk to the man
He will complain that you've been gone too long make sure you have space in your party though

Answer 3

1. Fly to Oreburgh City
2. Walk/Run in the mining museum.
3. There will be a scientist behind the counter, talk to him.
4. Select the fossil that you wish to be extracted.
5. Walk outside the building and walk back inside.
6. Talk to the man behind the counter again.
7. And you will receive your fossil Pokemon!

Hope I helped!