Right click on this link and pick 'save target as' or your browser's equivalent, or if you are comfortable with registry editing, you can read it directly and just make the change that it shows. Otherwise, once you have saved the file down just double click it in windows explorer and agree to merge it to your registry. Then reinstall the game via Stardock Central and you should have the French version.

Note that this applies only to GC2 itself. Dark Avatar has not yet been translated.

Thanks for all !
The traduction is very well !