On Ereb Rosh Hashanah, just as on every Ereb Shabbat and Ereb Yom Tob, women light candles and recite a Beracha. The Beracha recited when lighting candles for Rosh Hashanah is the same as for other Yamim Tobim – "Asher Kideshanu…Le’hadlik Ner Shel Yom Tob."
Some women have the custom to light Yom Tob candles only when the husband returns home from the synagogue, just before the Yom Tob meal. It is preferable, however, to light candles eighteen minutes before sundown, just as is done on Ereb Shabbat.
There are different customs regarding the recitation of the Beracha over the candle lighting on Ereb Shabbat. Hacham Ovadia Yosef maintains that women should follow the view of the Shulhan Aruch and recite the Beracha before lighting the Shabbat candles. Some, however, follow the opinion cited by the Ben Ish Hai (Rav Yosef Haim of Baghdad, 1833-1909), in Parashat Noah, which requires lighting before reciting the Beracha. According to this view, by reciting the Beracha over the candle lighting a woman already accepts Shabbat, and will thus be unable to light a candle thereafter. She must therefore ensure to first light the candles and then recite the Beracha. This is also the view of the Rama (Rabbi Moshe Isserles, Poland, 1525-1572). The accepted Halacha, as Hacham Baruch Ben Haim ruled, is that each woman should follow her mother’s custom in this regard.
However, as Hacham Ben Sion Abba Shaul (Israel, 1923-1998) notes in his work Or Le’sion (vol. 3, 18:1), this applies only with regard to the Shabbat candle lighting. When it comes to candle lighting for Yom Tob, according to all views a woman should first recite the Beracha and then light the candles. After all, it is permissible to light a candle (from a preexisting flame) on Yom Tob, and thus even if a woman accepts Yom Tob by reciting the Beracha, she is still allowed to then light the Yom Tob candles. Hence, even women who are accustomed to lighting the Shabbat candles before reciting the Beracha should ensure to recite the Beracha before lighting the Yom Tob candles.
Some women have the practice to recite the Beracha of "She’heheyanu" at the time when they light the Yom Tob candles, and this practice indeed has sources on which to rely. However, Hacham Ben Sion writes that it is preferable for women not to recite "She’heheyanu" at the time of candle lighting, and to instead fulfill their obligation by listening to this Beracha’s recitation at Kiddush and reciting "Amen."
Summary: Women should light Yom Tob candles eighteen minutes before sundown on Ereb Yom Tob, as they do on Ereb Shabbat. Even if a woman generally lights the Shabbat candles before reciting the Beracha, when it comes to the Yom Tob candles she should first recite the Beracha and then light. It is preferable for a woman not to recite "She’heheyanu" at the time of Yom Tob candle lighting, and instead listen to the Beracha’s recitation at Kiddush, though those who do recite it at the time of candle lighting have sources on which to rely.
