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Right click Setup and click Edit, which will open Fluent. You'll be presented with the Fluent Launcher – allocate a good portion of your cores to the Solver to help speed up simulations (I've allocated 16 of my 24 here).
Under General, select Density-Based (for supersonic CFD; Pressure-based for subsonic).
Under Models, select your preffered model for each part of the phsyics. For high-speed CFD (Reynolds No. > 10^6), Invsicid is a strong first option to get an estimate of forces and moments. When one runs Viscous CFD, meshing becomes exponentially more important (and complex) as the boundary layer must be resolved. Turn on Energy for supersonic flow.
Ensure the fluid is Air, as an ideal gas, as shown below:
