David, if the structure is identical, then UNION is your best bet.
You do that from the Data Source tab in your workbook.
That assumes that you can't just append the 2017 data to the existing 2016 data source.
As long as you are using Tableau Desktop 9.3 and above you could UNION the dataset. There is a good guide here Combine your data with Union in Tableau 9.3 | Tableau Software if you wish to do this
Hope it helps