Plugin used only on some pages – not widget

I solved id by myself.

For those who want do the same trick:
go to bliss-facebook-likebox plugin folder, edit cool-fb-likebox.php.
Near the bottom of file there will be an $url variable.

Change:

$url = urlencode($get_cfbl_options['fbpageurl']);

to:

wp_reset_query();
global $post;
$site-id = 1; // use your own needed number

if( is_page($site-id) || $post->post_parent == '.$site-id.') {
    $url = urlencode('https://www.facebook.com/pages/Your-Fanpage');
} else {
    $url = urlencode($get_cfbl_options['fbpageurl']); //editable in plugin options
}