How to connect floor monitor to mixer - Behringer XENYX 2442FX Mixer

Connect the two Behringer B215XL to the Right/Main Speaker Outputs. Monitor(s) would connect to the Left/Mon Speaker Outputs
manual is here: https://assets.peavey.com/literature/manuals/xr684fand696f_manual.pdf

why are you doing this?

An external equalizer will not help this at all. The problem is likely within the amp (feeding the main speakers), the connections from the board to the amp, or the speakers themselves. In other words, the answer would be "NO." Best of luck!

Without more information of your speakers and amps we can't really help you. The Mackie board puts out line-level signals and that should drive any connected amp or powered speaker to the full capability. Make sure you are using BALANCED interconnect lines either XLR or TRS cables. Use of TS unbalanced cables costs you 6 DB and also noise pickup. Make sure ALL your gear, amps, speakers etc are powered from a SINGLE receptacle or power conditioning module. Normally you will use the AUX outputs of the mixer by way of TRS cables or balanced lines in a snake to power amplifiers onstage which then connect to the stage monitors. If you have powered monitors the returns of the aux to the stage go to the powered monitors. A heavy duty extension cord brings power back from thee stage power to the mixer.

You will have to have an amplifeir between them since the PV12M is an unpowered speaker. The Xenyx 2442FX is likewise an unpowered mixer meaning it cannot directely drive a speaker. You will wire with a balanced line (TRS cable) between the 2442 and the amp and then from the amp to the speaker using a speaker type cable.

Judging from your mixer, I would connect your stage monitors to your SUB outs. Your mixer has 4 of them, allowing you to make 4 separate mixes to 4 monitors.

Yes you can - but do not use the loudspeaker outlets on the rear panel.
There are a variety of outputs on the front panel (bottom right as you look at it).
You can use the main output,  or monitor  send - (for monitor you may need to use the relevant 'send' switches on each channel to send signal to these outputs. 
You should also turn the power amp switch to main only (not main + monitor) so that the internal power amplifier is not connected to the monitor socket
You could also use the record out RCA (phono) sockets on the Peavey to connect to the CD / tape input on the main mixer.
You can download a pdf of the manual from here for more informationhttp://www.peavey-eu.com/index.php

DO NOT connect your in-ear monitors to the power amp out using the MAIN/Mon speaker option as it would be goodbye hearing and fried ear buds..
Get a very small and in-expensive headphone amp and connect its input to the 1/4 inch Monitor output jack.

Please read a tip I just posted regarding a hazard of the Speakon to 1/4 inch cables when used with these PMP mixers.

If you are using your main speakers as stereo, then you will need either powered monitor speakers OR an additional seperate amp for them. The mon outputs on the mixer are LINE LEVEL and are not driven by a power amp. Use TRS (balanced) interconnect cables from these to POWERED monitor speakers.

You can parallel your two mains providing the parallel impedance is 4 ohms or greater (two 8 ohms in parallel at most). The the monitor speakers can be paralleled and the switch set to Main/Mon so that one side of the power amp drives the mains and the other drives the monitors.

To prevent damage to the mixer, make sure all speaker leads are secure before powering the system. Run the speaker leads through the handles of the speakers to prevent inadvertent unplugging due to personell tripping over cables.

DO NOT use the bridge mode in your use.

The monitors will have to be POWERED monitors with built in amps.

You can simply use a wye splitter cable to drive the two monitors. Run the cable from the mixer to one monitor and put a wye cable and an extention to the second powered monitor speaker.