To add a new language to an existing user experience level, head over to the Control Panel, under the Data Types section, click on Manage User Experience Levels.
The list of existing user experience levels will appear, you can search for the user experience level you want by scrolling through the list or entering the user experience level title in the following field.
If you want to add a new language to an inactive user experience level, click the Selected View field and switch to the view you want.
Click the 'Pencil'-icon.
The following dialog will appear, click the Language field.
Select the language you want from the list.
After selecting a new language, you must enter the user experience level title again in either the default or the new language.
Click the Update button.
Click the OK button, and you are done.
When the user experience level is set to multilingual, a list of supported languages will appear as below.
Note:
1. Ensure that you are a User with 'Administrator'-rights set up to be able to access Control Panel.