To unlock the different towns available, you will have to collect a certain amount of medals. Depending on each town, the number of medals may vary.
Within the map, you will be able to see all of the available towns as well as the number of medals needed to unlock them. The map is in the upper right-hand corner of the game's main screen, represented by a planet Earth icon and a blue location pin.
For more information about medals, we recommend the following article: "What are medals and what are they for?"