Complex sentence: Her appointment with Birmingham City began in March 1993, when only 23 years old, and in 2002 became the first woman to hold such a post in the top flight of English football when the team was promoted.
Split into simpler sentences: Her appointment with Birmingham City began in March 1993, when she was only 23 years old. In 2002 she became the first woman to hold such a post in the top flight of English football when the team was promoted.