About User Interface Translation
Even though you have built all of your forms in a language other than English, you may find that some parts of your application are still in English. These text strings, which include the text for error messages , the log-in screen, and menu optionsand other default responses, are called "user interface strings." It is possible to translate these for each application, or to use translations that other people have used for your language.
...
If you are deploying your application in multiple languages, then you will need to add user interface translations for each language.
Editing User Interface Translations in Bulk
You can download all existing translations to excel. Click "Download messaging translations".
You can then translate the messages into your desired language, but be aware that CommCareHQ doesn't support accents in these messages and they will have to be left out.
In addition, in order that your translations are uploaded, you will need to put them in a column labelled with your desired language (see example below).
If If you now try to download the messaging translations, you will find your translated version along with the previous default language (likely in english)
Finally, on the language list page, you you will need to add your desired language and then make it the default language.
For French users, it's here the CommConnect UI translations are here: translations.xlsx