Dolomites to Lake Como

Take the train from Bolzano to Milan.
From Milan you can take another train to Varenna which is one of several towns on Lake Como. It depends on what town.

Depends on where you are staying in the Dolomites. It is a large region with connections sometimes made difficult by passes. Lake Como is also larger with many options. Where, exactly are you staying at either end?

Laurel, we will be in Santa Cristina in Val Gardena and then going to Varenna.

Then what Jazz said is right. You can take a bus to Bolzano courtesy of the bus pass your lodging will give you for the duration of your stay. A taxi, if you want that service, will be about €130.

Thanks, Laurel...and Jazz.