You will see a three vertical dots located in top right of the screen. Tap on it, you will see an option of countries for edition, e.g. "Australia edition". Tap on it, you will get a list of countries. When you roll up and down with your fingers on the list of countries, you can tap on a country to select the one you want. Now you have just changed to the country edition you want. It is the same way as you select a country as news source.

Please also see Q5