The Ashkenazi custom is for women to light the candles first, cover their eyes, recite the blessing, and then uncover their eyes to have enjoyment from the lights.
The reason for this is that ideally the blessing, like all blessings for mitzvot, should be recited before performing the mitvah itself (lighting the candles). However, there is a concern that once the blessing is recited it may be considered an acceptance of Shabbat and then it would be prohibited to kindle a flame. Thus the custom developed to light the flame first and cover the eyes while reciting the blessing. This is considered as if the blessing has been recited before kindling the flame. (Rema 263:5 and Shulchan Aruch 263:10)
Sephardic women do indeed recite the blessing first and then light the candles. (Rema ibid.; Ohr L’Tzion 18:3)
