Hi Gregg, to add more map Layers you need to drag a new or duplicate Makepoint calculation onto the visualisation pane.
If stuck, I wrote a 3 post blog series for Biztory on getting started with Map Layers, here: www.biztory.com/blog/tableau...
biztory.com
Tableau Map Layers: Getting Started (1/3)
Learn how to leverage Tableau's Map Layers feature to create complex visualizations, including advanced bar charts, by bending the rules of geographical plotting.