From the Santa Maria Novella train station:

from any train's track take your right hand EXIT, go down the stairs and turn right again, go straight to the end of Via Luigi Alamanni, at the end of via Alamanni you'll cross our Avenue Viale Fratelli Rosselli and turn left for 50 meters.

From Florence Peretola Airport by Bus or TAXI:

 You can take the shuttle bus "VOLA IN BUS", which will take you to the main SMN train station and follow instructions same as if you arrive by train.

http://www.aeroporto.firenze.it/en/the-passengers/transport/bus.html

By Car:

Coming from North/Milan, take the A1 Bologna - Florence , exit Firenze Nord , then follow the signs to the center of Florence, SMN train station .
- Coming from Genoa or France , take the A12 to Viareggio , and follow the A11 to Florence , exit Firenze Nord . Reach the center of Florence/ SMN train station .
- Coming from Rome , A1 Rome - Milan , Florence South exit , here following the signs to the center of Florence / SMN train station .