Auto throttle - when?

So the cl650 is my first plane with auto throttles. I’ve done 2 flights in the plane so far. 1st flight didn’t use the auto throttles at all landed fine. Second flight…nah. Used at the whole way and ended up stalling and crashing when I cut it off at vref. So my question would be this: when do you guys who use them cut yah auto throttles off, and if you got em on past the FAF, what speed are you setting?