Now that you have added one or more custom languages, you can specify which language a particular user will see in their view of the Control Panel. For this:
- Make sure that the required locales are added in Settings > Configuration > Interface Locales field. Unless you add the locales in Settings, customers will not be able to switch locale.
- Go to your Control Panel's Users and Groups menu.
- Click a user's name.
- On the page that appears, click the Edit Profile tab.
- Choose your custom language from the Locales drop-down list.
- Click Save.