If you come by car, you can find parking space in the rue Rodo, or in the rue Dancet. Else, the parking of the Plainpalais shopping center (Migros) is about 100 meters away, and the Coop parking is about 150 meters away. Both are accessed from the rue Dancet and are open around the clock.
If you use public transportation, the two following stops are less than 200 meters away:
Uni-Mail: 1, 15, 17, 32
Pont-d'Arve: 1, 12, 13