There are four ways of specifying the location, 3 of which involve knowing your latitude & longitude. If you don't know, this QTH locator can help you find your Maidenhead grid square or latitude/longitude. The first way is to use a Maidenhead grid square. Using this approach, you would enter FN31pr to get a map centered on ARRL headquarters. For a map around Acton, London (where I once had the pleasure of living), enter IO91um. Washington DC is FM18lv.

The second way is to use a latitude/longitude pair as two real numbers separated by a comma. A positive number for latitude means north, and a negative value means south. For longitude, negative means west, and positive means east. Using this approach, you would enter 41.714775, -72.727260 for ARRL headquarters, and the London example is 51.50471, -0.26781.

The third approach involves entering the latitude/longitude in degrees, minutes, and seconds. Enter up to three natural numbers separated by spaces followed by a character indicating north or south for latitude. Longitude is up to three space separated by spaces followed by a character indicating east or west. For ARRL headquarters, enter 41 42 53N 72 43 38W, and for Acton, London, enter 51 30 17N 0 16 4W.

The fourth way is the enter a city name. For big cities like Chicago, Paris, and London, you can enter the city name all by itself. For smaller US cities, enter the city comma state (e.g., "Pittsburgh, PA"). For non-US cities, enter the city comma country (e.g., "Caracas, Venezuela").