This is described at paragraph 2.2.2 of the User's Guide, available through FastHenry2's help.
In summary, you have two modes:
1. Single frequency
Run FastHenry2 with the default options, and you should have an output file in the same directory of the input files, named Zc.mat
You can use now the utility MakeLCircuit.exe that you must launch from a DOS shell, giving as argument the Zc.mat file:
C:\>MakeLcircuit Zc.mat
You will get a Spice netlist corresponding to the Zc.mat inductance matrix calculated by FastHenry.
If you want it in a file, to be imported by a Spice simulator, just redirect the output to a file:
C:\>MakeLcircuit Zc.mat > my_spice_netlist.cir
2. Multiple frequencies ('wide' band)
Specify a value for the order of the reduced order model (-r option), changing it from zero to the desired order.
This will automatically generate the file "equiv_circuitROM.spice".
You can also select to exit after generating the Spice model with the -M option flag (you save time because you don't need then to calculate the impedance matrices if you don't need them)
Best Regards,
Enrico