Lay a thick carpet on the stage at the back center. Putting a carpet down is standard practice when the stage is wooden as it prevents the drum kit from sliding about.
Stack two milk crates or bottle crates for every guitar amplifier. This elevates them from the ground and prevents vibrations from the amps from spilling into other microphones. It also raises them to a convenient height so that the guitarists can make adjustments without stooping down.
Set up a microphone stand for each guitar amplifier. Position the collar of the microphone stand in the center of the speaker, about a half inch from the grille. Set up a microphone stand for each singer.
Set up two microphone stands, one at each side of the drum kit. Extend the telescopic arm so that the collars of the microphone stands are higher than the kit.
Attach a clip-on microphone collar to the rim of each drum. Slide a microphone inside the bass drum. Most bass drum skins have a hole for this purpose. If not, put the microphone on a stand and position it as close to the front of the drum skin as possible.
Connect an XLR cable to each of the microphones. Connect an instrument cable to the "input" jack of the direct injection, or "DI" box. Connect the other end of the cable to the "line-out" jack on the rear of the bass amp. Connect an XLR cable to the "output" jack on the DI box.
Connect each XLR cable to an XLR jack on the mixing desk or mixing desk patch bay. A patch bay is a remote routing hardware device that eliminates the need to have cables running everywhere. Treat the patch bay as you would treat the inputs on a mixing desk.
Run a sound check. Have the band play and as they do, adjust the slider dials on the mixing desk. Set the sound levels so that the singer is clearly audible over the rest of the band.