This is Wes, the developer of this plugin. I am very sorry you are having trouble. I am sorry this has not been responded to, but I have honestly not logged into wordpress.org for almost a year. I do not fully keep up on the tickets posted to this forum.
In regards to your question, CSS is a relatively simple subject in it's most basic form. Also, in regards to styling a website, it is the minimum level of knowledge to be able to do any modifications. So, when I built this plugin, I added this feature as an extra for advanced users.
If you are interested in learning more about CSS I reccomend http://css-tricks.com. Especially his early tutorial videos. Beyond this site there are literally thousands of tutorials out there, just google for "basic css tutorial" or something like that.
As for "asking for donations", I am not asking for anything. I published this work free of charge. If people find it useful then I wanted to offer them the ability to give back. If not, then no big deal, use it for free. As an avid contributor to Open Source Software I can say that I have given almost as much work away for free as I have gotten paid for, and this is common for most of the people who publish wordpress plugins. So please be considerate of our work that we are offering here for free to help you.