Samantha is worried about her younger sister Emma, because Emma is a high school senior who just turned 18, and is still a virgin.
Emma doesn't want to be virgin, she just is too shy to talk to boys. The two sisters talked, and the two of them have decided that Samantha will help Emma get some experience, and hopefully some confidence. Samantha doesn't trust teenage boys, though. That's where you come in. You are Ian. You are a man Samantha knows through a mutual friend, and she thinks you'll be just right to help Emma.