Custom CCS to change margin in widget – one section only

I am displaying an image on my sidebar using the Image(JetPack) widget. I would like it to be centered in the space and not use the default margins for the sidebar. Is there any Custom CSS that would allow me to change the margin for just one section of the sidebar? (The same thing happens if I use a text widget and paste in the code) Website: http://sacredheart.org/School/