Well I don't know this module, since it's from a theme. Have you tried to make a second link group? Same settings but, sub-links alignment to center? Maybe you can use on display on (align center). thats probably even better.
If this is not working you have to edit tpl files.
For the image you need a image editor. I am no more too much into this, but some years ago GIMP was the best free tool. Maybe now days something like https://pixlr.com does the trick too.