The leak appears to be where the drain stem connects to the sink. The stem should have a flat piece with a washer, and a wedge pressing up against the top of the stem secured by the tightening screw.
The whole assembly unscrews. Open it up and examine the parts, should be able to see the source of the leak. You can purchase a replacement assembly or individual parts at any hardware store, who can go over with you how to reassemble. No difference than what you would find under any kitchen sink. Note-take a piece with you as it may be 1 1/4 inch or 1 1/2 inch plumbing.
Also YouTube will have all sorts or videos. Just search replacing kitchen sink drain plumbing.