WPML allows each user to have a different admin language for WordPress. I’ll show how to determine this and set the locale so that WordPress admin displays correctly in each language.
Site languages versus admin language
WPML allows WordPress sites to run in different languages. This means that one language becomes the default language and other languages are added. So far, nothing new.
By default the default site language is also the admin language.
Without WPML, you can set the site’s language by setting the WPLANG variable in wp-config.php. When WPML is enabled, the WPLANG variable is ignored. Instead, WPML sets the site’s languages.
Visitors see the language according to the page they’re viewing. Admins can choose in which language to administrate WordPress. The default is to have the same language, but it can be changed.
Choosing a different Admin language
First, you need to put WPML into Advanced mode. To do this, click on Go Advanced at the top of any page in WPML’s menu.
Go to WPML->Languages. Then, scroll down to where it says Admin language.
You can choose any of the site’s languages there. Once set, WordPress admin pages will appear in that language, unless users select a different language for themselves (up next).
Individual admin language per user
If you’re running a multilingual site, it’s very likely that different authors would like to see things in different languages. WPML makes that possible.
Each user should go to the profile page (Users->Your profile). Scroll to the bottom to where it says WPML language settings. There are several settings there and right now, we’re interested in the admin language.
Look at where it says Select your language. The default value is to use the default admin language (which we just set before).
This setting is per user and whatever each user selects here doesn’t influence other users. Any user can select the admin language, which overrides the default values.
Making WordPress display correctly for each language
In order for WordPress to display correctly in different languages, you need to have the localization files installed and the correct locale selected per language.
WPML comes with default locales for most languages, but you need to install the localization files for WordPress.
To do this, go to WPML->Theme and plugins localization.
You can choose one of the two options, to use .mo files to translation by WPML. When you will see a table with locale values per language. This table will already include the correct locales, as WPML determines, but you can edit it.
WPML shows you if the .mo file for WordPress exists in the wp-includes/languages folder. If it says File exists, it means that WordPress admin will display in the correct language. Otherwise, you need to make sure that the .mo file is in place and that the locale code (Code field) is correct.