Even using a translation app like google or bing, it's still hard to understand. As far as I can tell, the part of the article about changing the theme color is just pasting a file that you downloaded, into the GTK directory. But I think you have to somehow open it, and choose the one you downloaded. Somehow, you have to access the GTK options for your system, and choose the one you downloaded. It will change the theme for your entire system, as far as I can understand. Since I use Windows, I couldn't tell you how to find those options on Linux.
But usually there is a way with wordpress blogs, to post comments. Maybe you can contact the author, and ask them for help, using the Comment section at the bottom of the article?