BuddyPress.org

WordPress sends emails automatically to the admin (you I presume!).

If you are not getting those mails when you create users in wp-admin, then your mail isn’t configured properly in WordPress (as with ‘freeriders’ system in the thread I gave you).

You need to fix that before proceeding with BuddyPress install.

Look in the WordPress Codex for details on setting up / configuring the mail settings.