Passing on the Traditions

A married woman customarily lights two candles and may add an additional one for each of her children. An unmarried girl should light one candle in deference to her mother.

A soon as a  young girl can understand the idea of Shabbat and can say the blessing (approximately 3 years old) her parents should provide her with a candlestick and reach her to kindle the Shabbat Candles.