Once you have enabled either of the density-based solvers in FLUENT, you can activate the wet steam model (see Section 23.6) by opening the Multiphase panel and selecting the Wet Steam option.
Define Models Multiphase...
This section includes information about using your own property functions and data with the wet steam model. Solution settings and strategies for the wet steam model can be found in Section 23.14.5. Postprocessing variables are described in Section 23.15.1.