Turnigy 9x Pit Trim adjustment

[Burnt Toast]

Hi All , well I have this set, but im tring to set up the pit trim to use it as a channel to adjust a fuel mixture on my glow motor .
just woundering which channel the servo needs to be put in to .
as I have tried all that are spare , and have had no joy .
the servo goes ( I checked that )
is there something that Im missing ?