traveling to Varenna

Train. Malpensa Express train from the airport to Milano Centrale, then a train to Varenna-Esino. Since both trains are operated by Trenord, you can buy your tickets at the Malpensa train station. They are unreserved regional trains, so no need to buy in advance. Should take about 3 hours, assuming you have an hour wait at Milano Centrale.

Sam's post has all the information you need - if you are arriving at Milan Malpensa airport. If you are arriving at Milan Linate, or at Bergamo (which some airlines also call "Milan"), the directions would be different.

From Linate airport, you would take a bus or taxi to Milano Centrale station, then the train to Varenna-Esino. From Bergamo airport, you can take a bus to Bergamo station, a train to Milano Centrale, then the train to Varenna-Esino; or, you can take a bus right to Milano Centrale, then a train to Varenna-Esino.

From Bergamo there is no need to backtrack to Milan; there is a regional railway link to Lecco, where you can change to the train to Varenna (only a few stops).

We are arriving at Malpensa airport. Thanks for the information. It was very helpful.