I would recommend you to use our Header banner functionality instead of the default WC Store notice.
Please follow these screenshots http://prntscr.com/lkp7ro + http://prntscr.com/lkp7yv + http://prntscr.com/lkp84u + http://prntscr.com/lkp8fq add content into static block appropriate to your needs. It is simplest way because styling of content can be changed using WPBakery Page Builder instead of custom css coding.
