You can create a new foreign supplier from the 'Suppliers' submenu in the menu on the left or from Fast Input when you process an invoice.
Via the left-hand menu, click on the plus to create a new supplier. Via Fast Input, first open the invoice for which you want to add a new supplier. In the menu on the right, click on 'Create new supplier'. You will see a number of input fields. To view the complete supplier file, click on the square with the arrow in the top right corner.
Now fill in the pop-up sheet with the details of your supplier.
Please note: for foreign suppliers you should always check the following:
You can fill in the other fields as you would for a domestic supplier. Don't forget to click 'Save' at the bottom to save your data.