I looked up your mixer amd power amp and there is a main out and a monitor out section on the mixer with seperate eq for each.
So hook up your 15's or 12's to main out.
Then use 2 trs or ts cables as your monitor out jacks are unbalanced anyway.Keep EM short if you can. 3 feet.
Hook those from monitor out L/R on your mixer to L/R in on the power amp.
TURN THE MONITOR OUT VOLUME ON THE MIXER TO "0"
Start with the power amp volume at 1/2 and then bring the monitor out volume on the board up slowly till you see where your at.