Every order comes with as many polishing cloths as jewelry pieces ordered. If you want more of them you can order them here.

With a polishing cloth you can easily remove oxidation by firmly rubbing it over the surface of your silver piece.
The cloth will turn black by using it, this means it's working! Never wash it, as the polishing product will wash off and the cloth will lose its effectiveness. 

Please note that although gold-plated pieces also come with this cloth, using it might rub off the gold layer.