Add language to Windows 10
1. Click on the Windows 10 Start Menu (the bottom left of your screen) and start typing "language". When the "Language settings" link appears, click on it.
2. Under the heading "Preferred Languages" click the + sign to "Add a preferred language".
3. Type "french" in the input field and select Fresh (Canada)
4. After a few moments, Windows will find the language pack and you may click "install".
5. Your new laguage pack is now installed and a toggle button should be added to your system tray (bottom right corner of your screen).