Connect a speaker cable to the input jack of each speaker in the house system. Connect those cables to the "Speaker Out" jacks on the mixing desk. Desk layouts vary, but the "Speaker Out" jacks are typically on the right-hand side of the desk.
Set up one microphone stand in the front center of the stage for the singer. If there are any backing singers in the band, set up a microphone stand at the front of the stage, in front of the band member's amplifier.
Set up a microphone stand in front of each instrument amplifier, apart from the bass amplifier. The collar of the microphone stand should be level with the center of the speaker in the amplifier. Shine a flashlight on the amplifier to see the speaker more clearly.
Attach a clip-on microphone holder to the rim of each drum in the drum kit, apart from the kick drum. Set up two microphone stands to the side of the hi-hats. If the drummer is right handed, the microphone stand goes on the left and vice-versa. Adjust one stand so the collar is level with the top hi-hat cymbal. Adjust the second stand so that the collar is pointing downward, toward the other cymbals.
Slot a microphone into the collar of each microphone stand. Connect the female end of an XLR cable to the bottom of each microphone. Connect an extra XLR cable to another microphone, and slot that microphone through the cut-out in the front of the kick drum.
Connect each XLR cable to an XLR socket on the mixing desk, one microphone per channel. Mixing desks typically have 24 channels, so there will be sufficient connections. As you connect the wires, write the source sound on the wipe-clean strip at the bottom of each channel strip so that you know which channel operates which mike. Use abbreviations to save space. For example, "Gtr 1."
Connect an instrument cable to the direct-injection, or "DI" box input. Connect the other end of the cable to the "Line Out" jack on the rear of the bass amp. Connect a second cable to the output socket of the DI box, and connect the other end to an instrument cable jack on a spare channel strip.
Run a sound check. Have the band play a song while you adjust the volume level for each sound source. Move the gain slider dial for each channel up to increase the volume level and down to decrease the volume level.