Connect the two main output speakers to the left and right output channels of the mixing console.
Connect the third (and/or fourth) speaker that will be used as a monitor to the auxiliary outputs on the mixer. This will be marked “AUX,” “Booth” or “Monitor” on the mixer and labeled on the connections on the back of the mixer. You might need a one-quarter-inch TRS to XLR or RCA to XLR adapter to make this connection.
Once you have your speakers connected, turn on the mixer. Turn on the speakers.
Set the output levels for the CDJ, laptop or turntable to your main outputs by turning up the main volume fader.
Turn up the monitor or booth send (fader or knob) in the main mixing sub of the mixer. Set a reference level just below 0dB for sound check.
Turn up the monitor channel send (fader or knob). This is most often above or near the EQ potentiometers of the channel strip.
Adjust this send up until you hear it in your third monitor speaker. You may need to adjust the auxiliary send up and down to achieve an appropriate monitor level.
Connect one speaker to the left main output of the mixer. Looking at the stage, set this left main output speaker on the house left side of the stage (stage right in theater parlance).
Use a long XLR cable to run to a second speaker in the back of the room on the left side. If the room is much bigger than a small club, you may need a delay unit to synchronize sound at the back of the room.
Repeat the same process for the right main output of the mixer.