By train
Sirmione is located near the Milan-Venice railway line, but there is no Sirmione railway station. Arriving from the West we recommend you get off at the Desenzano station, while arriving from the East we recommend you get off at the Peschiera station. In both cases, you will then have to take a bus to Sirmione.
As for train times, we refer you to the website of the Ferrovie dello Stato.