Centering images in widgets

Hello, I’m using the ‘team-member’ circular images in the ‘testimonial sections. I only have three images to use and they are showing up left aligned. I would like them to be centered horizontally within the testimonial section and am not sure where to do this. I looked at the source code and can see that it says col-sm-3 and am thinking that I should change that to
col-sm-4 (so 3 images would fit) but cannot find where to make this change. Any help would be greatly appreciated.