¿Como poner el slider de la home del prestashop al 100% de la pantalla?

Te vas a la ruta del servidor themes/classic/assets/css/custom.css 

Y añades…

body.page-index #wrapper .container{max-width:100%;width:100%;padding-left:0;padding-right:0}
body.page-index #wrapper .featured-products,body.page-index #wrapper .banner,body.page-index #wrapper #custom-text{margin:0 15px}
@media (min-width: 992px) {
body.page-index #wrapper .featured-products,body.page-index #wrapper .banner,body.page-index #wrapper #custom-text{max-width:940px}
}
@media (min-width: 1200px) {
body.page-index #wrapper .featured-products,body.page-index #wrapper .banner,body.page-index #wrapper #custom-text{max-width:1140px}
}
@media (max-width: 991px) {
body.page-index #wrapper .featured-products,body.page-index #wrapper .banner,body.page-index #wrapper #custom-text{max-width:100%}
}
.carousel-control .icon-prev,.carousel-control .icon-next{margin:0}