For starters set all your speakers to small in the receiver setup speaker menu. Set the Crossover to 80hz on the receiver for all speakers to start, you may experiment later with other settings. Set the crossover on the back of the sub to bypass (if this option is available), otherwise, turn it clockwise to the max to get it out of the way for the receiver to handle.
Run the test tones on the receiver and adjust all speakers and sub to 75dB from the seated primary position holding at ear level pointing straight up. When adjusting the sub levels, I would put the receiver around -2 to 0dB level, and just adjust the main volume on the back of the sub up/down until you reach the 75dB.
For the SPL meter, put the dial on the 80dB selection, C -weighting, and slow speed.
this should give you a good start.
