featured slider to be centered

using the lucid theme from elegant themes, i’ve moved the featured slider call from the page template to the header template in order to get the header bg to extend behind the slider. unfortunately i thus lost the centering for the slider and now it looks like this: http://www.lacasasanmarcos.com/meditationretreatperu/

i’ve tried “text-align: center” and “margin: auto” in a few places, but can’t seem to affect the positioning. the fact that the theme is responsive doesn’t make it easier (even tho it’s appreciated of course).

any ideas?
thanks to all!