You can display up to 64 cities at a time on the World Map. To add one or more cities on the map, open the Add/Remove City window from the Map menu. When you open the window, you will see a list of cities available. This is not all inclusive list but comprehensive enough.
Add city on the map
Choose one or more cities from the available city list. You can use the mouse and shift key or just double click on the city you wish to add. After selecting the cities, click on the "Add to map" button. Selected cities will be added to the "Selected Cities" list below the available city list. Click "Apply the change" button and you will see the cities you have selected on the world map.
Remove city from the map
If you wish to remove certain cities from the world map then select the city and click on the "Remove from map" button. Once you finish removing the required cities from the list, click on the "Apply the change" button and you will see that the selected cities are not displayed on the map now.