The most entertaining way to move around the lake and arrive to Cernobbio is by boat! You can check out the boat schedules on the website provided. The boats are comfortable, accurate and exciting! At least for me!
Probably, in my opinion, the easier way to come and visit Cernobbio is by boat.
You can take a pubblic (they are really nice) boat from Como (see) or other lake cities.
It's faster and cheaper than bus.
Cernobbio is connected to Como and to all the towns on the western side of Lario (i.e. the lake of Como) by very frequent buses.
You will arrive or you will take your bus in this square.