so flow is from left to right?
i'm not sure i understand the goal, the goal is to see the pressure at the exit? what are your inlet and boundary conditions? inlet flow and exit pressure, as such the output will be the pressure at the inlet.
i don't think i understand your question about something being full of fluid. are you talking about the second or third screenshot?
and what result are you seeing that is wrong? have you set the min and max of your plot so you can see the pressure better?
have you gone through the tutorials and validation examples? i seem to remember there being an example that you could use.