Plug one end of a TRS cable into the "Send" jack on one of the power amp's mixer channels and plug the other end into the "Input" jack on the effects processor.
Plug one end of the other TRS cable into the "Output" jack on the effects processor, and plug the other end into the "Return" jack on the same power amp's mixer channel.
Plug your instrument or microphone into the "Input" jack on the same mixer channel. You will find that the signal coming from your instrument is processed by your effects processor, with none of the original "dry" signal remaining. This setup will work for effects processors that are meant to alter the entire signal, such as equalizers, compressors, limiters, noise gates, or wah-wah pedals.
Plug one end of a TRS cable into the "Effects Send" or "Aux Send" on your power amp's mixer, and plug the other end into the "Input" jack on the effects processor.
Plug one end of the other TRS cable into the "Output" jack on the effects processor and plug the other end into the "Effects Return" or "Aux Return" jack on the effects processor.
Plug your instrument or microphone into the "Input" jack on one of the power amp's mixer channels, and use the "Effects" or "Aux" knob to adjust the amount of effect that is added to that particular channel. This setup does not alter the entire signal; it just sends a bit of the signal through your effects chain and returns the altered signal to the mix, to be added to the original signal. This works for effects such as reverb, fuzz, flange, or any kind of tape delay processor.