OnlineHelp: Vehicle configuration
At the top of this panel, you select the type of aircraft you are flying, and the rest of the panel will be populated appropriately.
Once the proper aircraft type and subtype has been chosen, select the appropriate motor channels at the bottom of the screen.
If the default Mixers do not suite your fram, you can switch the vehicle type to Custom (current mixer values are kept), and from then on you can define additional mixers.
In order to assign an output to a PWM buzzer or any "servo-like" accessory just have a look at User Guide: Direct Transmitter Passthrough