Running the FX from the board into the monitor mix will require a stereo breakout cable - 1/4" stereo on one side splitting out to left and right 1/4" connections. 

1.  Connect the stereo end to the FX OUT jack on the back of the X2442USB.2.  Connect the left and right TS jacks of the cable into the left and right 1/4" inputs of a stereo channel of the mixer (9/10, 11/12, 13/14, or 15/16).3.  Make sure the FX send on that stereo channel is NOT turned up, as a feedback loop will result!
4.  Press the MAIN button on the stereo channel to route the FX to your main output.5.  Set the Aux 1 send on the channel to PRE-FADER6.  Turn up the Aux 1 send on the channel to send the FX to the monitors.7.  If you are using a second monitor mix, turn up Aux send 2 on the stereo channel.Always make sure that the FX send on the stereo channel is turned down, otherwise a feedback loop will occur which may cause damage to the mixer, not to mention your hearing.