Public transport: ATM

If you want to use the bus, tram or metro you should first buy a ticket. You can't buy one in the bus, tram or metro. There are several tickets, you can check them here.
To plan your journey you can fill in the addresses here and it tells you what to do.
If you're staying for a longer period in Milan, you can get a subscription with a card to travel. For this service you require a 'codice fiscale' (which you can get at one of the 'Agenzia delle Entrate", often you need this code as well for other contracts).