When the Gemara says "Hanachah" Oseh Mitzvah, it does not mean that "one must place it down" after lighting every time he lights it, but rather that (1) it must be resting at the time that he lights it, and not held in his hands (22b), and that (2) it does not need a new lighting when it was lit improperly. Placing it down alone is sufficient.

(You may have been bothered by the Gemara's statement that if Hanachah is the Mitzvah, one cannot light from one wick to another, implying that lighting alone is not the Mitzvah until one does a Hanachah. However, I do not think that the Gemara means that. Rather, it means that according to this opinion, the Mitzvah is having it lit -- that is, after the lighting has been done -- rather than lighting the candles -- that is, the act of lighting itself.)

-Mordecai