There are now language packs available for all 12 of the supported ClassicPress languages. These can be downloaded here: Languages – Classic Commerce
Each zip file contains one .mo and one .po file. These files should be uploaded to the wp-content > languages > plugins folder on your website (you may need to create the folder).
These files are based on the corresponding WooCommerce language files and some Classic Commerce translations may be missing or incorrect. Please report any omissions or corrections here.