The entrance to the Botanical Gardens can be found at
Largo Cristina di Svezia 24
00165 Roma RM
Image credit: Google maps
From the North (P. le Clodio, piazza Cavour) or the South (P. le Ostiense, v.le Aventino):
reach ponte Sisto with the bus lines 23 or 280, continue by foot along via di Ponte Sisto, via di S. Dorotea, via di Porta Settimiana, via Corsini.
From the centre (p.zza Torre Argentina) or the West (Monteverde, Trastevere station):
reach p.zza G. Belli with tram 8, then continue by foot along via della Lungaretta, via della Scala, via di Porta Settimiana, via Corsini.
Parking:
There is paid parking for cars along Lungotevere della Farnesina and there are the paid-for underground car parks of the Janiculum and of via Giulia.
Link to google maps