Slider centre

Hi i know you have a post on centre align slide that I read and tried code but hasn’t worked and i have just checked my mac book pro and slider not centred and looking weird. Im not sure how to fix it. Is there particular place to paste code outside of style.css or header.php?

http://www.slinkyhairdressing.com.au/

Kindest regards,

Kon

https://wordpress.org/plugins/easing-slider/