Once a MODFLOW simulation is saved, MODFLOW can be launched by selecting the Run MODFLOW command from the MODFLOW menu. At this point, if the MODFLOW simulation has not been saved, GMS will prompt you to save the simulation. MODFLOW will be run using the simulation in memory.
If GMS is using the ModelWrapper, a dialog appears and you will see some text output reporting the solution progress. If the ModelWrapper is not used, you should see new DOS window reporting the solution progress. When MODFLOW is finished, you can return to GMS and read in the solution.
Related Links:
MODFLOW Interface
MODFLOW Model Checker
Saving a MODFLOW Simulation
Post Processing
MODFLOW Display Options