BuddyPress.org

I added link with function.php But how i set custom link (http://forum.site.com) for that?

/**
 * adds the profile user nav link
 */
add_action( 'bp_setup_nav', 'add_calendar_2_bp_nav_item' );
function add_calendar_2_bp_nav_item() {
	global $bp;

	$args = array(
		'name' => __( 'Study Hall', 'buddypress' ),
		'slug' => 'http://site.com',
		'default_subnav_slug' => 'my-study',
		'position' => 24,
        'screen_function' => 'bp_nav_tab_stuff',
		'item_css_id' => 'my-study',
	);

	bp_core_new_nav_item( $args );
}