Dear George,
it is of course possible to run FEFLOW interactively using an IFM module. However, for a start it might be easier to use PEST or FE-LM2, depending on your needs. The latter is directly integrated into FEFLOW and accessible via the tools menu entry (Start parameter fitting ...). A lot of additional details are given in the FEFLOW documentation. PEST has to be loaded as an IFM module.
Kind regards,
Wolfram