It's very easy. We had 2 large bags and 2 small bags so we took at taxi both ways. The cost was 35 € each way. Took about 15 to 20 minutes. If you don't have a lot of luggage it's only a short walk from the train station to Piazza San Marco and there you can catch the local bus Number 7 to Fiesole or vice versa. Cost of bus was under 2 €. Buses are frequent about every 20 minutes. Bus ride 15 to 20 minutes.
Buongiorno, le rispondo ben volentieri. Sì i collegamenti con l'autobus sono ottimi. Se ben ricordo ci vogliono circa 20 minuti per arrivare direttamente in centro a Firenze. Le auguro un buon soggiorno.