Add space between portfolio images on front page

Hello, I'm trying to do the same thing as below in css for my portfolio images on front page. I currently have two rows of three columns and cannot seem to find the right code to add. (below) example is for featured content) @media screen and (min-width: 48em) { .featured-content-wrapper.layout-three .hentry { width: 33%; } } .featured-content-wrapper.layout-three article { margin-right: 2px; }