Turn the volume on your Line 6 amplifier down to zero. Turn the master volume on your PA system down to zero.
Turn your guitar's volume down to zero. Plug your guitar into the amplifier using a 1/4-inch guitar cable. Plug a 1/4-inch guitar cable into the line out jack on your Line 6 amplifier.
Plug the other end of the 1/4-inch guitar cable into the input on the PA system head unit. Turn the Line 6 amplifier volume up to the desired amplitude. Turn the PA system master volume to the desired amplitude.
Turn the volume on your Line 6 amp down to zero. Turn the master volume on your PA system down to zero.
Plug your guitar into the amplifier using a 1/4-inch guitar cable and turn your guitar's volume down to zero. Plug a 1/4-inch guitar cable from the line out jack on your Line 6 amplifier into the proper input on the snake cable. The snake input correlates with the channel your guitar runs through on the PA system.
Plug the snake cable into the PA system's mixing console at the desired channel for the guitar. Normally, the drums occupy the first third to half of the channels on the mixing console, followed by the bass and then the guitar.
Turn the volume on your guitar fully up. Turn the Line 6 amplifier volume up to the desired amplitude. Turn the PA system master volume to the desired amplitude.