For most flow simulations in Autodesk® CFD, we neglect the weight of the column of liquid in determining the pressure distribution. For cases in which this weight is important, particularly when the fluid is at rest or when moving at a constant velocity, enable Hydrostatic Pressure on the Physics tab of the Solve dialog.
When solving for Hydrostatic Pressure, a gravity vector is needed, so be sure to specify the Gravity Method and Direction. The resultant pressure gradient due to the weight of the fluid will be in "down" direction, as specified by the Gravity Direction.
If natural convection is also a consideration in your flow, you can also enable Heat Transfer. Note that hydrostatic pressure and buoyancy can run concurrently, but depending on temperature gradients, the effects of one or the other may be masked by the other phenomena.
Hydrostatic Pressure cannot be enabled for Free Surface simulations. If you enable both, (either for a new simulation or a restart), an error message appears to indicate that both are enabled and one should be disabled before proceeding.