139:10 The time to light Chanukah candles is immediately after the stars appear, and one should not procrastinate. One may not do anything before lighting, not even learn Torah. (Not only that, but if one starts to do something, he must stop doing it in order to light – Mishnah Brurah 672:10.) If one has not yet davened maariv, he should first daven and then light. Before lighting, one gathers the members of his household in order to publicize the matter. One must put enough oil in his menorah to enable the candles to burn for at least half an hour. (If one does not have enough oil to last this long, he should light without a bracha – Bi’ur Halacha 672:2 s.v. b’zeh hashiur.) After the fact, if one did not light immediately, he may light with a bracha so long as the members of his household are still awake (until daybreak – MB 672:11); once they have gone to sleep, there is no publicizing of the miracle so he would light without a bracha.
If one will not be able to light at night, he can do so earlier, lighting from “plag hamincha” – which is an hour and a quarter before the stars appear – or later. This is measured in “sha’os zemanios” – “seasonal hours” calculated by dividing the daylight hours into 12 portions. On Chanukah, the daylight hours are short so if the length of a day is 10 clock hours, then plag hamincha will be one hour, two and a half minutes. One may only light early so long as he puts enough oil in his menorah for his lights to burn until half an hour after the stars appear. If the lights do not burn this long, the mitzvah has not been fulfilled.
139:11 The order of lighting Chanukah candles according to our practice is as follows: On the first night, one lights the candle to his right. On the second night, he adds another candle to the left of the first one. On each subsequent night, he adds an additional candle to the left. The newest candle is lit first, continuing to light to the right.