The app is fairly straightforward: using Google Maps, you can pinpoint your location or select most major cities. Next, you can select the size of the bomb, using either kilotons, or referencing notable bombs from history. Finally, you can select exactly what type of information you want, including casualties and fallout effects. Pretty grim.
On a week like this week, it's important to remember what has happened in the past. Hopefully, mankind has learned from our mistakes and the type of destruction projected by the NUKEMAP remain just those: projections.