How do i apologize to my dad?

Well you never specified WHAT exactly you were appologising to you dad for, but I'm assuming it's to do with the underage drinking and 'manipulating' your step-mother. Maybe just approach him when he's not busy and say that you're really sorry and you realise that what you did was wrong and you wont do it again. He was a teenager once, he'll understand and forgive you. Dads are like that. Hope I helped!