how to add shadow effet to the slider – theme Customizr

How to add shadow effect to the slider on Customizr theme ?
I’ve found the css code below but dont know how to apply it to the slider.

.box {
  position: relative;
  width: 400px;
  height: 300px;
  background-color: #fff;
  box-shadow: 0 1px 5px rgba(0,0,0,0.25), 0 0 50px rgba(0,0,0,0.1) inset;
  border-radius: 0%     0%     25%     25% /     0%     0%     3%     3%;
}
.box:before {
    content: '';
    position: absolute;
    z-index: -1;
    bottom: 15px;
    left: 10px;
    width: 50%;
    height: 20%;
    box-shadow: 0 15px 10px rgba(0, 0, 0, 0.7);
    -webkit-transform: rotate(-3deg) skew(-0deg);
     -moz-transform: rotate(-3deg) skew(-0deg);
     -ms-transform: rotate(-3deg) skew(-0deg);
     -o-transform: rotate(-3deg) skew(-0deg);
     transform: rotate(-3deg) skew(-0deg);
    }
.box:after {
    content: '';
    position: absolute;
    z-index: -1;
    bottom: 15px;
    right: 10px;
    width: 50%;
    height: 20%;
    box-shadow: 0 15px 10px rgba(0, 0, 0, 0.7);
    -webkit-transform: rotate(3deg) skew(0deg);
     -moz-transform: rotate(3deg) skew(0deg);
     -ms-transform: rotate(3deg) skew(0deg);
     -o-transform: rotate(3deg) skew(0deg);
     transform: rotate(3deg) skew(0deg);
    }