Content Importer - how can I import existing translations into the corresponding language layer for the source already in Tridion?

Hi all,

New user, we're trying to import translations for a source already in the en-US layer.  From what I gather the translations need to have the identical GUID but be marked xml:lang='xx-XX in the concept tag?

eg. <concept id="GUID-394A57GG-C75C-4833-AFAD-981E08D0D8DD" xml:lang="nl-NL">

Is it this simple, as long as the translation files match the xml structure of the source?   So far, I have not been able to do this using content importer, the imports only update the en-US layer?

Thanks!

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