This amp is unusual - there is no trim pot and no individual channel clip lights that I can see or that are mentioned in the manual. The instructions in the manual (not well explained) seem to be to connect up each channel in turn, and turn the (rotary) fader up until the level out of the amp seems OK. Repeat for each channel.

The monitor send refers to a separate Jack out at line level, not to the monitor output section of the amp, which is just one half of the stereo output.

Stu