Go to Shipping Settings
From the merchant portal, choose Settings from the navigation menu, and Shipping from the dropdown menu.
Choose a Country
Find the section for Rate Rules, and press the Add Country button. If there are currently no countries present, then the section will prompt to create one.
If there are already countries added, then the button is on the right labeled + Country.
A country can now be selected by typing the country you are going to restrict in the entry field, and then press the green Add Country button. If you want all countries expect yours to be restricted, type Rest of World into the entry field.
Add Shipping Rule To Restrict A Country
At bottom right of the selected country tab, press the green Add Country Rule button.
A dialog box will appear, and you will have the ability to choose the Restrict this Country rule.
Once Restrict this Country is selected, press the green Add New Rule button to save your rule. Checkouts will now be restricted for this country.