Depending upon how much luggage and/or tired you are, you can take the Express Bus from MXP into Milan. It takes 40min-1hr and stops at the central train station. From there, there are frequent trains to Cumo. From the Cumo train stop it's about a 5-10 min walk to the lake/boat dock, where you'll find a variety of boats giving tours of the lake with stops at the many towns situated up and down Lake Cumo. It is a beautiful lake, and if you have the opportunity, don't miss it. As for Milan itself, I found it a very easy and enjoyable city to walk around in, with lots of interesting sights / restaurants/ shopppes etc.