WPML language negotiation to "languages in different directories"

Hello,
I am trying to use BuddyPress Multilingual to add Arabic language my site.
I installed BuddyPress 2.2.0 and BuddyPress Multilingual 1.5.
I am getting this error message;
For BuddyPress Multilingual to work you must set WPML language negotiation to "languages in different directories".

How to do that?

I appreciate your time.
Plz see attachment.
Thanks again,
George