1) Prepare a speech or something about how much you love her and bring a ring and something that the girl will like
2) Take her somewhere private and romantic, give gifts
3) Profess your love once more through speech
5) (If she does not reciprocate this, back off she is not ready)
6) If she did reciprocate, present ring and ask her to marry you
7) If she does not shut down to avoid talking to you, you have won