Turn on the mixer, audio amplifiers and any other equipment connected to the mixing console. Make sure all audio cables and devices are firmly connected to the appropriate connectors on the back of the mixing console.
Set the mixer's master volume at "0" to start. Start with channel one on the mixer and set the channel's gain knob and volume fader to zero. Press the channel's activation button, usually situated above the volume fader knob. The gain knob filters how much of an audio signal goes to a specific channel. Think of the gain knob as a gatekeeper in this respect.
Instruct someone to speak into the microphone, or play the instrument associated with the channel. Slowly turn up the gain knob until the digital or analog volume meter on the mixer is picking up a solid audio signal.
Slowly turn up the volume fader on the channel until the desired amount of volume is coming from your sound system's loudspeakers.