The easiest way to get going is to use the pre-made slides along the bottom of the viewer.
Mouse over the viewer window and they show up. Click on a slide to change the zoom and layers that are visible.
Move around the scene using the tools on the toolbar in the upper left OR your mouse.
The home button takes you back to the initial extent of the map. In the case, it is the state.
Zoom in and Zoom out
Use the pan tool to drag the map around.
Use rotate to rotate the map as well as change the angle.
The compass icon displays rotation. Click the button to return to north.
Use the scroll wheel (if you have one) to zoom in and out.
With the pan tool selected, left-click, hold and drag to move around the map.
With the rotate tool selected, left-click, hole and drag to change the rotation and the angle.
Click the layer list button in the upper right to show the layer list. Layers with a check mark are on and visible in the map. Uncheck any layer to turn it off.
Note that layers draw from the bottom to the top so the top-most layer that is checked will be fully visible and may hide layer beneath it.
Use the Zoom To button to zoom to the full extent of that layer. Most layers in the Viewer are statewide.
Click on the basemap button in the upper right to change the basemap. The basemap will draw underneath all of the other layers in the scene.
The measure scene tool is really amazing because it allows measurement even in the 3D scene.There are three options on the tool:
Measure Distance, Measure Area and Slice Objects. The ArcGIS Online help for Measure scene is thorough so head over there for the details.
Click on the Daylight icon to change how sun angle and shadows change the scene during different days and time of day.