How to connect Echo/delay/repeat to mixer that enable me to setup/control all 12 channels on my mixer

Check the inserts and pan controls.

Why are you not using the inserts? Either assign a sub channel to your effects unit or do it at a channel level. In either case using the insert.

Good luck. Your mixer only has one aux out to supply only one stage monitor out. Only way to make it work would be to use the panning controls of each channel to different outputs to the Left and Right main outs for stage monitors and aux out as front of house speakers. I would get another separate mixer for monitor such as another efx 12 with every input connected to both mixers, then use the panning and main outputs to that. Sorry. Just not enough of mixer. You need an aux out for each individual's monitor.

Can't find a manual but can still explain. Delays, chorus, flangers, and reverbs are all the same effect except the different names of them will allow you different adjustments. Chorus usually has a width control which controls pitch shifting. Flangers and delays will have a feedback control which simply means, how many times you hear the echo. On reverb units, room size means how long of echo(even though it;s short) you want. Delay is the same with much longer echo, feedback is the same as on flangers except the flangers time is very short meaning the effect is at almost the exact time resulting in feedback causing a metalic sound. I probaly just confused you but good digital delays usually have all the features and will usually do all 4 effects depending on how you set them. If you want delay, set width on 0 and adjust time and feedback. For flanging, adjust width and speed and feedback. Chorusing, adjust time, width, and speed. Reverb, adjust time, set width on 0, and feedback. I see it has a level(mixture, how much effect you hear), and a replay(feedback, how many times you hear it), and a delay knob,(how long the echo will be) The range/mode switch allows for settings of diferent time lengths and INF setting allows for infinite repeat. Hope this helps.

You will need to buy an effects unit for this, either delay or reverb depending on the echo you want, there are no built-in effects on this mixer, sorry!

Hope this helps!

The Efx 12 has two outputs monitor out as well as mix out ( XLR sockets ). If the level bars are moving its an indication that the mixer is working. Have you tried headphones out as well as monitor out.
What is your amplifier and speaker setup- you have not mentioned it at all.
Even if any PFL switch is on you won't get sound out of the speakers.
PFL stands for Post Fade Listen and when any of the 12 channel PFL switch is on only the headphone out put will work.

View videos on YouTube regarding "mixer setup". Find the parts of setting up of "effects". Don't worry that you have a different mixer, the principles are all the same for analog mixers. Steps are this: Set the EFX send level for EACH of the input channels (knob above each channel gain) for the proportion you want for each channel. Check that the level you are sending does NOT cause the effect clip light to light very much. Set the effect you want, delay, echo, etc. with the selector knob. Advance the output sent to the power amp with the two knobs in the upper right of the panel. Adjust the "time" knob for the delay or effect depth you want. Then go over the same settings in the same order until you get the sound you want.

Visit this link to download the manual if you don't have it already. https://phonic.box.net/shared/crqxhlhmmz
This mixer has a multi-effects processor onboard, but the key is understanding the audio signal chain. There is a chance that you have your input audio going through an undesired effect, but without knowing your setup (input source, connections, mixer settings), it would be difficult to pinpoint the problem.

Run your speakers cables to your stereo "outs" (L/R) then run your sub off of one of your aux "outs" or sub group "outs" (make sure you assign channels to sub group out).

Usually delay is associated with "reverb" not echo. If you are in a large room, the room acoustics can add reverb without the benefit of signal processing.

Reverb NORMALLY passes the inout signal as is and then adds in a delayed version on top.

The delay should be less than the room size delay.

Try turning off all effects as a start. There is some "transport" time if it goes through a digital signal processing.