Who in your family is Costa Rican, and how did they get it?
Born abroad, you can claim only through a parent who was Costa Rican by birth: born in Costa Rica, or born abroad and registered. A parent who naturalised does not pass it on, except to children who were minors living in Costa Rica at the time. If you are unsure which your parent is, their Registro Civil entry says. A grandparent counts only if the parent in between was registered.