Mackie CR-1604 mixer: how to get stage monitor audio to Behringer B205D powered monitor speaker

[KeyOfCee]

I have a plain old Mackie Design CR-1604 - 16 channel mixer connected to two powered PA speakers from left and right MAINS that are working good.
I've got 2 keyboards (each in stereo) with 4 inputs going into the Mackie onto channels 13 thru 16. We are using channels 1 thru 4 for vocals.
I want to connect a Behringer B205D powered speaker to the Mackie and use it as a stage monitor (vocals, keys) separate from the L/R MAINs.
I've been looking in the manual but I'm just not getting it. I'm no sound guru by no means. I'm a keyboard musician just trying to figure this stuff out and it's frustrating.
I'm missing something but I just don't know what. Any help from anyone knowledgeable about this stuff would be greatly appreciated.

[Jazz P Bass]

Without digging up the manual, I would suggest that you try using the Aux Out feature.

[KeyOfCee]

I tried Aux 1 but I can’t seem to get any sound from it. Even when I have Aux 1 routed to monitor I still have no sound.
Now mind you, I have 2 stereo keyboards going into channels 13 thru 16 using 1/4 in unbalanced from the keys to the rear XLR male into XLR female on the XLR 10 mic input expander (which is part of the CR-1604).

[Randall]

I get paid to do sound gigs. I do not make sense of your second sentence above, but if you have keyboard sound thru your mains, this is not an issue. Your Aux 1 send is your monitor send, this is basic stuff. Connect your monitor to AUX SEND jack. Then adjust your levels with the AUX 1 knobs on channels 13 - 16. Then adjust your AUX MASTER knob. There are probably a couple of switches next to the AUX MASTER knob that you may need to try different positions.

No disrespect intended, but this is a guitar amplifier repair and maintenance forum, not Sound 101.

[nevetslab]

If' you're not getting any output from Aux 1 Send jack (above Mic 4 input connector, rear panel), try Aux 2 Send. Note you can push the Solo buttons below the Aux 1 & 2 Send Masters in the master section at the top right of your board, just to be sure you're getting signal (using headphones).

[The Dude]

Aux 1 is switchable to pre or post fader with the MON button directly under the aux 1 level control of each channel. In one position, you'll also need to have the fader up to get signal out of the aux output. In the other position, the fader won't matter. Typically monitors are prefader so that adjustments to the mains don't effect monitors. Is it possible you have the switch in the post fader position and the fader is all the way down?