if you wish to add a question better to open a different thread,
anyway, to use Prode (or a different simulator) as first step you must define the stream (list of components, fractions, thermo models etc.) then in nozzle.xls you define Tin, Pin, Pout and mass flow,
the program calculates the required area and estimates t out,
models are applicable to both single (including dense phase) and two phase flows.
Different variants are possible (i.e. design, rating etc.)
For PSV modeling I prefer HEM which gives conservative values (in two phase flow),
the other models (HNE , HNE-DS , NHNE) are applicable to specific cases
and if you are not sure imho better to use HEM,
note that Prode includes a rigorous HEM not the simplified Omega method.