Demo Page 6

How can I make 3 boxes like demo page 6 with icons on the top from the shortcode creator button. I see full-width boxes and the 1/3 option but I am unsure how to set the margins and the icon. I know you set the margin first but I am not sure how with the shortcode generator. I do see the full-width option on the drop menu but when the box populates the icon field is blank and does not generate anything. Am I supposed to know the code for the icons?

Regards,

Robert