You get 1 War dollar if you aided in the defeat of a continent for that round, you get 2 War dollars if you land the finishing blow(i.e. Africa attacks Antartica, Europe attacks and defeats Antartica;Africa gets 1 war dollar, Europe gets 2 War dollars).
A round starts with one continents actions and keeps on going until every continent has had a turn to make a WoMD or restore a city. Then a new round starts.
If you have any questions or anything PM me. Have a good game!