To get started, navigate to Appearance > Elements > Sticky bar:
By default, a dismissed sticky bar will be hidden for 7 days. You can change that by using the option "When closed, re-open after".
Make sure the jQuery library is loaded, to do so, insert this code snippet in the functions.php under WordPress Appearance menu > Theme Editor:
add_action('wp_enqueue_scripts', function() {if( ! wp_script_is('jquery') || ! wp_script_is('jquery', 'registered') ) {wp_enqueue_script('jquery', 'https://ajax.googleapis.com/ajax/libs/jquery/3.1.1/jquery.min.js', array(), null, true);}});