Is there manual of mounting a apm copter

hi, i am new of this field. i want to diy a six propeller copter with apm 2.6 board. is there any manual of that?
and i can not find the source code of apm copter in the download page. where to get it? does apm planner provide the firmware?

The manual or Wiki is located here:

Source code is here:

But I don’t think you want to monkey with that. The APM Planner does have the compiled stable firmware to load directly on the board.