Follow the yellow ! for the quests.
If you do not have any yellow ! then you ca do anything for now.
If I remember correctly, the next night you should be able to get the wine and talk to the target.
Ah, I see!
In that case, a bit of feedback; you may want to add a little text blurb from the bartender that I should return later, otherwise it's not obvious that it's even possible to do that (until you leave anyway; I thought the bar thing was a one-time event, so I tried to avoid leaving until I had "finished" it)