Start with you. Add a profile for your parent who is the descendant of Olivier, then add a profile for the grandparent who is the descendant of Olivier, then add the great-grandparent etc. As you go double check to make sure the person you're adding isn't here already. If they are, you may discover cousins here at wikitree. Eventually you will "meet" a profile that is listed on Wikitree who is a descendant. I see he has six children listed at wikitree, I didn't check for his grandchildren etc. It is important to add sources for the information you add, things like birth certificates, death certificates, census information, wills, that prove relationships and facts.