Can someone PLEASE help me?

Two days ago, I met a lovely girl named Janelle who I am extremely attracted to. I have been distant friends with her brother Angelo for a few months now, and I have been contemplating the possibility of asking Janelle out. She seems to like me, at least as a person, because she smiles at me a lot, but I can't seem to actually talk with her in a conversation. How do I attract her to me? What do women like in men? Oh, and please keep in mind that we're both fifteen years of age. And how do I express my feelings without angering her brother?