Languages and Translations
Since WordPress 3.7, it’s been easy to get BuddyPress in your language. WordPress will automatically download a translation for BuddyPress for the language that your site is using.
If you’d like to use BuddyPress in another language, but your WordPress site is still in English, you first need to configure WordPress to use another language. Learn how to do this here. Once that change is made, WordPress will download translations in the new language for both itself and BuddyPress (and for many other plugins).
If you’re an advanced user and want to download a translation manually, or just view a list of all available translations, see the project page on translate.wordpress.org.