How do I use the map viewer?

Using the legend:

Use checkboxes to turn data layers on or off. For the best representation of overlapping layers, view layers one at a time. Slide the toggle bar in the legend to change the transparency of map layers. You can hide or expand the legend with the top left icon.

Viewing the map:

The top right icon will pop out the map in a new window and make it larger.  Use the +/- buttons to zoom in or out.

See this tutorial for a demonstration.