To unscrew that lense, either use a piece of hard rubber - like an eraser, or use your finger....press down on it firmly but gently, and turn counter-clockwise to unscrew it. Now, take a tiny amount of your favorite lense ceaner solution and GENTLY wipe off the lense. Sometimes it is best to not use your finger, as I think most of those lenses come with an AR coating that may get screwed up from the acidity of your fingertip.