Hi paulcobb,
Thanks for using Menu Social Icons!
Menu Social Icons doesn’t set any margin or padding for your icons —?that comes from the CSS of whichever theme you are using. Without looking at your specific site, it’s difficult to give you the exact CSS, but you should be able to find the correct CSS selector quickly using Firebug or Chrome Developer Tools.
For example, in Chrome, right click on one of the icons. Here is a screenshot that shows what happens when I inspect one of the icons in TwentyTwelve: It shows the CSS selector that is used by TwentyTwelve to set margin, and then allows you to try other values to adjust to your taste.
Once you identify the correct selector and margin or padding value that you would like to use, you can add your own custom CSS to override the theme by using a plugin like JetPack, Simple Custom CSS, or Custom CSS Manager.