Sometimes it’s the worst option, since traffic jams are quite common (130 km, a few euros in motorway tolls).
By train
From the airports there are shuttles almost every 30 min/1 hour to the railway station Milano Centrale; from there direct train to Morbegno (train Milano – Lecco – – Tirano), then bus (extra 50 min or so).
Trenord has an app “Trenord” (Bus iOS and Android) which works quite well and with which you can buy tickets.
If you travel late in the evening check the time of the last train to and from Milano Centrale, as well as the bus connection to Valmasino…or prepare for a bivy!