Resurrect Fossil Pokemon
Once you have the FOssil Pokemon of your choice, you will then have to resurrect it. As I mentioned before, yo resurrect them you will have to get to the Cinnabar Island which opens up quite far into the story.
Go to the Cinnabar Island and head over to Cinnabar Lab which is located left to the Pokemon Center. You will find a man in a Lab Coat around the Lab. Talk to the man as he will resurrect the Fossil Pokemon.
Which Fossil Pokemon to Choose
I understand that it can be a difficult choice between the Dome Fossil and Helix Fossil as you won’t know which one to choose. Here I will help you with that and will also explain the Pokemon they will be resurrected into.
The Dome Fossil is resurrected or revived as Kabuto who is a Rock and Water-type Pokemon. Kabuto will evolve into Kabutops.
The Helix fossil will be revived into Omanyte which is also a Rock and Water-type Pokemon. Omanyte will evolve into Omastar. For Comparison sake, Kabutops is faster in terms of Physical attacks but Omastar has better physical defense and HP.