Place the MX802 on a flat, level surface away from heat sources such as amplifiers. Connect the proprietary power supply cable to the rear of the unit and connect the opposite end to the power outlet. Ensure the unit is switched off.
Turn all the gain and volume levels on the mixer down to zero. Ensure that the Phantom Power switches, labeled "+48" are in the off position. Connect any microphones to the XLR sockets at the top of the first four channels. Connecting a microphone with the Phantom Power turned on can cause serious damage to it.
Connect all instrument cables to the 1/4-inch jack sockets at the tops of the remaining four channels. These sockets are grouped in stereo pairs; if you're using stereo instruments, connect to both the left and right sockets. For mono instruments, just connect to the left one.
Connect the stereo sockets in the top-right corner labeled "Main Out," to the output speakers or PA system. This will provide the master output, heard by the audience. Connect the "Control Room Out" sockets located just below the "Main Out" sockets to your onstage monitors. This will give you independent volume control over each, using the "Main Mix" and "Control Room" volumes, respectively.
Power on the mixer, play something through it, and gradually increase the "Main Mix" and "Control Room" volumes to the desired level.