On BuddyPress Multilingual you can read:
This plugin requires WPML. It uses WPML’s language API and hooks to BuddyPress to make it multilingual.
You need to have WPML installed for BuddyPress Multilingual to function correctly.
Also, Buddypress Multilingual is for Buddypress sites. If you want to make your WordPress site multilingual, my advice is to use WPML.