Help finding lost half sibling.

Good evening lovely ladies of glow. I need some help finding the best site to find a lost half sibling. Back when my dad was 17 he fell for a girl, they had sex, she got pregnant and as soon as she told her dad he shipped her into another state to live with her mom. Her and my dad lost contact after she moved. 8 years later my parents had me, and never spoke about it. A few years ago, my dad told me I was not his eldest and that I had a half sibling some where. now that I'm older I would like to try and make contact with them. And I have absolutely no clue how to go about it and no information on the woman my dad had the child with, or that child. If anyone knows how to do this, or knows the best way to do it I would greatly appreciate the help.