Latest version of Mystique theme already providing many social icons by default and also it allows you to easily add any new social icons. So if you’re using latest version of Mystique theme then no need to install this plugin ;)
If you are using WordPress and the Mystique theme, then the Mystique Extra Nav Icons Plugin will help you with adding additional social icons above the menu bar. This plugin allows you to choose your extra social icons at the top right side of menu bar via a drag ‘n drop interface. You can use this plugin to customize social icons on the top right side of menu bar. You can just drag ‘n drop your icons in the admin interface to customize them. It also uses image sprites to speed up the loading time of your pages. You can easily add your url for selected icon also option is provided to choose size of icons.
The screenshots of option of this plugin are: