1. To add a new language to Windows 10, first open the Settings app and select Time & Language from the options.
2. Under the “Region & language” section, click the “Add a language” button.
3. In the “Add a language” window, you will be presented with a list of available languages. Select the language you wish to add from the list and click the “Add” button.
4. Once the language has been added, it will appear in the “Languages” list. Click on the language to modify its settings, including the display language, speech options and handwriting recognition.
5. If the language you added is not yet installed on your PC, you will be asked to install it. To do so, simply click the “Download and install language pack” link.
6. After the language pack has finished downloading, the language should be installed on your computer and ready for use.
7. You can now set your newly added language as the default language, as well as set the language preference order.
8. To set a language as the default language, right-click on it and select “Set as primary”. To set the language preference order, simply drag and drop the languages in the order you would like them to be used.
9. Once your language settings have been configured, you will be able to use the newly added language in various applications such as Microsoft Office, web browsers, etc.