leaking sink drain
take the putty and roll it in your hands to form a snake about 1/4 "- 3/8" in DIA. then install it under your stem . then tighten your nut making sure not to distort the large rubber gasket, I tighten the nut until I see its seated correctly into the sink drain outlet. by then you should be left with about 1/16" of putty left under the drain. clean the excess up and you should be fine.
one important suggestion!. Don'T use the plumbers putty on anything other then Stainless,cast iron or steel. if its a cultured marble sink then silicone should be used to prevent spider cracks.