customizing individual widget

I am a newbie in this, and I am working on a site built with theme twentyfourteen. (http://www.aaaborsellino.com). I have a left sidebar widget, containing articles. I would like to emphasize the first (most recent) article e.g. changing some attributes (color, size or whatever). Reading some suggestion on Internet, it appears that, in order to do that, you need the name (id) of the particular widget, but this is not available: the articles are listed using the regular

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• ,…,

structure. I tried to use the plugin “widget css classes”, but it seems that I cannot access the individual widget to give it custom classes and id. Am I doing something wrong?
Sorry about my English, I am writing from Italy. Thnks in advance
Robert