[Plugin: Cyclone Slider 2] center images within slider?

How can I make the images center inside the slider? Currently, they are aligned to top left…

I have tried the following code in childtheme css, but it did not work ??

.cycloneslider-slide cycle-slide, .cycloneslider-slide cycle-slide cycle-slide-active {
    position:relative;
    margin: 0px auto;
    }