Addin margin to So Hero Buttons

Hi! I would like to know how I can add margins to the SO Hero Buttons. Do I need to install to install the CSS Editor or can I do it through the “Widget Styles”->”Attributes”->”Widget Class” & “CSS Styles”?
I also have to point out that I have 3 buttons no each slide, and there is a possibility for them to become 4. The margin is needed because in mobile devices (or small screens) the buttons do not have any space between them.

Thank you in advance