Setup the main speakers that will be used for the audience to hear the performance. You want them to be in front of the stage on either size. Depending on the size of the crowd, you may use to use many different sizes of speakers, or if there are only a few people expected, a simple single full-range speaker on each side may be efficient. Angle them away from the stage to prevent or reduce feedback.
Place the monitors on the stage or performance area. This will allow the musicians to hear themselves while they are on stage. Guitarists and bassists often use their amps for monitoring, but drummers and vocalists need the benefit of a good monitor to know what is going on during the performance. One per band member is sufficient for most concerts and performances.
Setup the main soundboard for the microphones and instruments. This mixing board will allow you to culminate the sounds from each instrument into a single stereo mix that will be amplified through the main speakers on each side of the stage. The main board should be placed far enough away for the engineer to hear the main speakers to make sound adjustments so that the band sounds pleasing to the audience. Soundboards come in many configurations from simple 4 track models to those that have 96 different channels for orchestras and bands with many instruments that will be used throughout the entirety of the show.
Connect the amplifiers that will run the monitors and the main speakers. Depending on the power needed, amplifiers come in different configurations and have a varied amount of power. From simple 100 watt amps to amps that push thousands of watts, your speaker amount will dictate the amount of watts needed for a venue. If you are running full range sound for thousands of audience members, you may need 6 to 8 amplifiers capable of pushing multiple cabinets each. Some smaller mixing boards have built-in amplifiers for small coffee house and subdued gigs.
Place microphones on guitar cabinets and drums as well as vocal microphones. You can plug them into a snake, which consolidates the amount of wires that need to be run to the mixing board, which can be many feet away. The snake has one large wire that contains many smaller wires and there is a box at the end that has many inputs, each input is marked and the individual wires can be plugged into the mixing board at the other end. This prevents audience members from tripping over the many wires required to capture the sound of an entire band.