Reversing any two power leads to the motor will reverse rotation. You will need two contactors; one for FWD and one for REV. Connect the top of the FWD contactor to L1, L2 and L3 in that order. Wire jumpers from the top of the FWD contactor to the top of the REV contactor but swap L1 and L3 so that the REV contactor receives the power as L3, L2 and L1. At the bottom of the contactors jumper out L1 to L1, L2 to L2 and L3 to L3 on the two contactors. Connect the three phase motor leads to the bottom L1, L2 and L3 of either contactor.
Your control circuit will then have to be wired STOP, FWD and REV and connected accordingly. Run one of the 120 volt control wires (call it #1) to the STOP switch. Then split off into two circuits on the other side of the STOP switch. The first split goes through the FWD pushbutton, through the Normally Closed auxillary REV contacts,to the FWD coil. The other side of the FWD coil is connected through the overload contact(s) to the other control wire (call it #2). You should now have FWD working.
The second split from the STOP switch goes through the REV pushbutton, through the Normally Closed auxillary FWD contacts,to the REV coil. The other side of the REV coil is connected to the same side of the overload contact(s) that the FWD coil is connected to. The other side of the overload contact(s) should already be connected to the control circuit (#2). You should now have REV working.
This setup will provide an electrical interlock to help keep both contactors from being energized at the same time.
A mechanical interlock between the forward and reverse contactors is highly recommended.
Hope this helps. Good luck and be careful.