Connect the Toneport to the computer using the USB cable. Power on the computer and select the Toneport as the sound input device. On a Windows PC, this is accessed through "Control Panel" and "Sound." On a Mac, this can be accessed by clicking "System Preferences" and "Sound."
Set up the band equipment in the venue as for a normal live performance. Place microphones in front of all guitar and bass amps, the kick and snare drums and a pair of overheads. Connect all microphones to the inputs on the PA mixer and perform a sound-check. Balance all the relative volumes of the instruments by listening to the mixer output with a pair of headphones. This will help block out the local sound of the band, allowing you to hear the PA mix.
Connect the RCA phono end of the hybrid cable to the "AUX" output on the mixer. Plug the 1/4-inch jack from the other end of the cable into the Toneport. Launch the recorder application and press "Record" as the band is playing. Turn the gain control until the input level dial bounces up to the red section, but not over into it.