Ok.
Here’s a quick and dirty routine:
1) play something, set your level meters on the C2 to PFL
2) use the gain knob on the channel to have the first red light on more or less permanently (0dB) and the second red light coming on at the peaks in the music
You know have it set to never exceed 0-2dB into the master bus with the channel fader full open.
Switch the level meter back to master.
Set your amp to full power (i.e. max. clockwise).
When you are playing make sure you never turn up your master volume higher than the first red light on the volume meter. This is 0dB into the amp. The amp should be geared to receive 0dB and play it without clipping or distortion.
Anything over 0dB from your master to your amp is at your own discretion.