Newbie Question about sink drain

Please look at the attached pic. I've got a stainless sink drain or whatever the correct term is on a new sink. The drain comes in two parts which screw together right below the threads visible in the photo. You can see a drop of water leaking through where it is screwed together. I got this as part of a discontinued faucet, with no instructions. I am getting a little leakage at the top of the drain where the plastic gasket is, as well as at the threads mentioned already. 2 questions:

1. Should I have used teflon tape where the two parts screw together?
2. Have I installed the clear plastic gasket correctly? It looks like it wants to pop out. I used the smaller gasket on the top side of the sink, putting the curved part down. I put the curved part facing up underneath the sink (seen in photo).

No teflon tape required as the seal comes from the rubber gasket. It looks to me like the washer is missing that goes between the gasket and nut. Thats why the gasket looks like its going over the nut.

Jerome - I wasn't referring to teflon tape at the gasket. Look at the photo and you can see a drop of water on the pipe just where the threads turn into smooth pipe. At this point the smooth pipe actually screws into the threads above it. That droplet of water came out of there, not from above. Maybe I need to find the manufacturer of this thing and see what parts are supposed to come with it. A washer around the gasket makes sense.

Ok sorry, then use either teflon tape or some pipe dope.

Yes, a wrap and a half of teflon tape where the fine threaded tailpiece screws into the body.

Strange looking mack gasket, but assuming it is correct, they are prone to allow water to travel down along the threads of the body. Take the nut back down, and using your thumb, mush some plumbers putty into the threads. Just enough so the threads are filled, but not bulging. Now screw the nut back up.

If there is a drip where the mack contacts the sink, use some silicone caulk.

As Jerome said, definitely seal the threads - they're never perfect. Also, I'm not sure about the topside gasket (as opposed to the underside gasket). I' haven't installed a ton of sinks, but the few that I have installed used plumber's putty between the drain and the sink. Maybe a gasket isn't out of the question, but it's just not what I've seen. It couldn't hurt to find the installation manual on the manufacturer's website just to be sure.

That is a VERY strange gasket on the bottom of the sink, so I would want to know what it looks like before it was installed. It may not even be the correct gasket for that location. A "close out faucet" would still have instructions in the box, unless it was a display model, in which case there is not telling whether key parts were missing since it would NOT have had to be watertight, just look good.

The washer under the sink goes on the other side. That replaces plumbers putty between the sink bowl inside and where you drop the drain down.
It doesn't go on the bottom, that washer should have been a thick rubber washer. Your're missing a part.

Where the threaded tailpiece inserts into the drain body, either pipe dope or tape.
You can also smear a little dope on large threads above to prevent water from running down the threads, not always needed, but sometimes.

I have to agree with Terry, that's the wrong gasket, I can't tell for shure with your picture but there should be a big washer on top of the nut.

Thanks guys. This drain was just loose in the store - kind of a frenzied close out situation. It was Expo Design, which closed, so maybe I'll take it down to Home Depot and see if they can figure out what it is.

Terry - there is another gasket which I placed on the other side of the sink. It is smaller than the one in the photo but the same otherwise. I think with all the comments I'll be able to find the right parts.

Regards