There should be threaded collars that attach the different parts of the drain plumbing. Sometimes you can stop a leak by just tightening the collar. Only hand tighten, you don't need a wrench.
If that doesn't work, there's a soft plastic half tapered gasket that the collar tightens up against. It's called a compression ring.
If it's leaking from the sink basket, there's another collar to try tightening, or replace the flat rubber gasket that seals it. Hope this makes sense to you.
2012 Jay Flight 19RD
2010 Tundra TRD DBL Cab
1 Spoiled Dog