Don't know why it didn't show up, but the ATM site/app is the best way to find your way around Milan. You can put in addresses or subway stations and it will plot out various routes via public transit.

I assume you know that some transit methods (trams and buses) only allow you to pay your fare via a pre-purchased card/pass, so you need to go to a bar/tobacco shop and purchase either individual bus/tram cards or a reloadable card.

Have a good trip!