It depends on which daughter board you are using, the ICM-20100 outputs 5V at about 20ma and would require a 5v low current relay coil. If you have a ICM-21105, then it will output 500ma at 24 volts. You can hook this directly to the 24V relay. Take a look at the Galil website, and download all of the manuals that you need.
For the VFD FOR/OFF/REV, connect to a Galil output through a relay(s). Connect the speed control to the analog +/- 10V CMD and GND signal for that axis per the instructions in your VFD manual.