Turn all the volume levels on your mixer to zero to prevent feedback, static or sudden noise while setting up your equipment. Plug in your mixer's power source and turn it on.
Connect your music source to the mixer by inserting one end of an audio cable into your music source's output or headphone jack, and inserting the other end of the audio cable into the mixer's input jack(s). Be sure you're putting the proper cables into their correct holes (sometimes the mixer's input jacks will be red and white for left and right audio, while other times the mixer will have a single input for all incoming audio).
Set up your PAs by twisting to the left the knob on the side of their poles, thus loosening the tripod legs. After spreading out the tripod legs, twist the same knob to the right, tightening the legs and locking them into place.
Connect the female end (the end with holes) of one of your XLR cables into the left master output of your mixer. Plug the male end of this same cable into your left PA's XLR input. Leave plenty of slack in the cable between the speaker and the mixer. Coil up the slack and place it aside to avoid tripping on the cable and stressing it, which over time will cause it to damage and short out.
Plug the female end of your other XLR cable into the mixer's right master output. Plug the opposite end of this same cable into your right PA's XLR input. Leave some coiled up slack and place it out of the way.
Turn on your music source, begin playing a song, and slowly turn up the master volume levels on your mixer to test your levels. If you're getting sound from the PA speakers, then you have successfully connected your DJ system to your PAs.