It is very easy to rate an article. Just select and click the corresponding article. All information available for the article (e.g. summary, tags, downloads, etc.) will be displayed. Next to the title of the article is a box with five white stars. To rate the article just move your mouse over the stars - they will change color. Once the desired number of stars have changed color left click with your mouse. The rating of the article goes up with the number of colored stars.