Before Kiddush, the woman of the house lights candles and recites two blessings: "to kindle the lights of the Festival" and Shehecheyanu.
If the Festival occurs on a weekday, she lights the candles after, or as soon as, it gets dark.
She says the blessings first and then kindles the lights. She should remember not to strike a match for lighting the candles, however, as she is accustomed to doing when she lights the Shabbat candles, but should light the match from an existing flame.
If the Festival occurs on Shabbat, she lights the candles while it is still day, before Shabbat begins, reversing the order of her actions.
She lights the candles first and then says the blessings. In her blessing, she makes mention of Shabbat as well: "to kindle the lights of Shabbat and of the Festival."
When she recites the blessing Shehecheyanu, she should bear in mind that this also refers to all the other mitzvot of the evening, just as the head of the household has this thought in mind when he includes this same blessing in the Kiddush.