BuddyPress.org

I am not sure in which sidebar you want to implement this.

If you are talking about blog sidebar in default BP theme.

1. Open sidebar.php from wp-content/themes/bphome/

2. Replace all content with following code

<div id="sidebar">

<?php if ( !function_exists('dynamic_sidebar')

|| !dynamic_sidebar('blog-sidebar') ) : ?>



<div class="widget-error">

<?php _e( 'Please log in and add widgets to this column.', 'buddypress' ) ?> <a href="<?php echo get_option('siteurl') ?>/wp-admin/widgets.php?s=&show=&sidebar=sidebar-4"><?php _e( 'Add Widgets', 'buddypress' ) ?></a>

</div>

<?php endif; ?>

<?php bp_adminbar_notifications_menu(); ?>

</div>

3. Check by clicking on any post from main blog.