I am not familiar with the spektrum line of radios but I am sure the manual talks about end points. It is simply the point your servo will travel to from center. If your radio is on and rx is powered up then your servo's should be centered (all but your throttle which will be where ever your stick sits). Endpoint is the end of the servo's travel in one direction. You can set both endpoints. Lower endpoint will be for idle and upper is for WOT. You don't want WOT at 1/2 stick or visa versa. Try to make your throttle move with each click of the stick until you have reached a good idle and top end. I am not the best at describing this but try like heck. Hope it helped.

Kevin