Set the volume knob to your usual listening level - it's hard to say '10 o'clock or whatever' as one does with stereo amps, because volume controls on AV amps tend not to work like that. Similarly volume displays may show an abstract number, or a -XXdB figure. so it's hard to tell you what that should read, too.
FWIW on my receiver normal day to day level is about -20dB to -15dB, so if your amp displays volumes in that way, that's not a bad place to start.
And again on some amps when the test tones are running the main volume control doesn't work - makes sense, as you can adjust the relative level of the channels without the confusion of changing the global setting halfway through the process. On others, you can adjust the main volume while the test tones are running.
Best bet is try the test tone for the first channel, see what the meter reads, and if it's way below about 75dB, turn off the tones, wind up the main volume control, and start the tones again.
Which receiver do you have?