Asteria Lite Slider

Hi all, I’m hoping someone here may be able to help me. Using Asteria Lite with a slider on first page I don’t seem to be able to alter the height of the slider on this theme. I’ve tried altering the size of the pictures but they just get displayed at the size dictated by the theme and just appear pixelated. I’m guessing I need to edit the theme code manually but I’m not sure where I find that>