Hello, usually the target spot can be pointed out by opening the Book [Tab key] , then while the desired quest is highlighted (main quest is highlighted by default upon opening the book) press Enter key or Left Mouse Button, Nishy will turn in the target location, plus a big blue beam will appear at the target spot.
For the Bar Idea, if you have talked with Blondie, then the Kelpie must be brought near construction spot which Nishy is targeting with a woman interfering. There's a spot (pointed out with Book) in a dark alley, in-between the nearby buildings.
I hope this helps,
Cheers,
~NK