What do I need to fix this leaky sink?
Plumbers putty , in a 3/8 in thick rope circle, goes under the top part.  

It helps to have a helper push it straight down and keep it from turning while the jamb nut and rubber washer and  (sometimes paper) thrust washer.  The rubber washer goes against the sink.  The thrust washer goes between the rubber washer and the jamb nut.

If someone used some thread dope previously, get the mating surface of the sink cleaned off.

If the rubber washer or the thrust washer is deformed, replace them. 

This video from Anaheim shows the mounting of the "Cushion ring" in step 6

A locknut wrench helps to loosen/tighten the nut.



This video shows replacing an ISE with a Waste King