Normally, you go to . Windows contacts Microsoft servers to download the pack ( .cab file) automatically.
Language Pack ISOs: If you have access to the Microsoft Volume Licensing Service Center (VLSC) or a Visual Studio (MSDN) subscription, you can download a "Language Pack ISO." This single file contains almost every language supported by Windows.
dism /online /add-package /packagepath:<path to language pack file> /norestart
Using :