Connect a four-pin speaker cable to the first output jack on the monitor mixing desk. The mixing desk is positioned at the side of the stage. From this desk, the monitor engineer controls the levels and balance of the monitor mix.
Connect the other end of the four-pin speaker cable to the monitor amp. This drives the speakers inside the stage monitors.
Connect a 1/4-inch jack cable to the output of the monitor amp.
Connect the other end of that cable to the input jack on the monitor. Some monitors have 4-pin jack inputs, in which case use a 1/4-inch jack-to-four-pin cable between the monitor amp and monitor.
Turn the "Master Output" fader on the mixer to zero. This protects the hearing of those in proximity. A faulty cable can cause buzzing to come from the monitors. If the output is set high when the amp is turned on, the musicians may be exposed to a loud blast of buzzing. At the very least, this is annoying and makes you look unprofessional. At worst, it can cause hearing damage. Mitigate this risk by minimizing the "Master Output" before delivering power to the monitors.
Turn on the amplifier. This delivers power to the monitor.
Increase the "Master Output" fader gradually. If you hear a buzzing as you increase it, lower it again and check all cables are correctly connected. If the cables are connected correctly, you may want to troubleshoot them one-by-one to see if any are faulty.