Best option is to come by car: If you have a navigator look for "località Torre del Castellano n.60, Reggello", otherwise use the A1/E35 highway and get out at Incisa-Reggello, first exit South of Firenze, and turn right keeping on the main road for about 2 km until you will see the Torre del Castellano (massif medieval castle) on the right; pass the castle and take the green gate in front of you.
You can also take the S.P.69 from Firenze or Arezzo and turn at the km XIV/III.

If you come by train you can arrive at the station of Incisa proceeding from Arezzo or Firenze and from there take a taxi (you will need to call by phone since only occasionally they park in front of the station).