Here you can manage countries and enabled countries are used in calculating the shipping, payment location and taxes. This Countries list page can be found under 

Log in to your admin panel and go to System> go to system> localization> country. Obviously, all countries are already on the list, so no need to add more! 

Let’s take a tour by exploring the setup of Country.

These countries can be used to estimate shipping and taxes when a customer enters their location. Each country can be individually disabled, removing them from the storefront, by editing them. The countries can be deleted as well. 

Note: The only problem with deleting a country is that the information of that country will be deleted.

You can edit the country by clicking the edit pencil button.

Checking an individual box in the first column will select the country within the same row. Once selected, you can choose to  "delete" the Country on the top left corner and click the "+" button to add new. 

Country Name:   Enter your country name
ISO Code (2):  ISO Code (2) Where you enter the code there places the country name.(example: US,IN)
ISO Code (3):  In this case, ISO Code (3) where you enter the code there places the country name. (example: USA, IND)  
Address Format:  Address format is the order of the customer info. so we use the address format on the checkout page. 
Postcode Required:  You need to select you made the postcode yes or no
Status:   Finally Enabled or Disabled the country status.

Finally, check that all the mandatory (*) are filled and pressing the 'Save' button in the upper right corner will save the information.

Let's look at how the website and app country list will be displayed, based on the country their state will be displaying 

Congratulations !!! Now your store country is enabled and you can use this in shipping/tax calculation to your store, which will help your customers make informed decisions before they make a purchase.