Thank you for writing in, to center a content on a Column, please inspect the column where the image is placed and then set the text-align option of that column to center. This will work with images,text, and custom HTML.
Images element has a width option, but I advise that you leave this as auto for a responsive reason.
Section width cannot be set though, because that is responsive, meaning it will respond to the screen width, you can apply a max-width CSS property though, so you can limit its width not to extend with the define width.
Hope it helps,