The basic throttle setup kind of goes like this. You have the throttl closed and the trim switch and throttle stick all the way down and the servo in the aft position. Then hook it up. Now the ideal scenario here is when you turn it all on. If move the trim switch all the way up, you;l be at a good idle area and the throttle will be fine.

So when you throttle all the way back, the engine will be at idle, then move the trim switch back and shut it off. This is how it should work and usually can with experience. Where you install the arm on the servo also effects travel. Don't read more into this than its worth, you'll figure it out.

On my computer radios, pretty much the same idea but one of the toggle switches on the TX is also a kill switch.