The ArcGIS app is a free download and can be found in the:
It may also be downloaded onto a smartphone from the ESRI 'Apps for Smartphones and Tablets' page.
Using ArcGIS Explorer
To find Department maps in the Esri ArcGIS Explorer app, search using 'ndgf'.
Note: You do not need to create an account when using this software on your smartphone. After launching the app, click on 'Continue Without Signing In' at the bottom of the screen.