How do I directly target CSS fixes?

Near goal: Need to remove the border on the social icons on I don’t want to take the image border CSS rule out because I want that rule for other locations on the site. I want to just exclude the social icons. I also want to add padding between the icons.

End goal: How do I generally target specific CSS rules? I’ve tried the Chrome Dev tools, Firebug, etc, and I just can’t seem to target exactly what rule I need to change CSS.