The ESC is programmed from the factory to have prop brake OFF.
TO PROGRAM THE ESC FOR PROP BRAKE: Turn radio and plane off. Turn radio on and put throttle at FULL throttle. Turn plane on. You will hear some tones indicating that the ESC is in "programming" mode. The first tone is a simple beep tone (with just one beep if I recall).
When it changes to a different tone/number of beeps (i.e., the SECOND type of beeping that is DIFFERENT from the first type of beeping - this second beeping is a triplet beep (e.g., dit-dit-dit) if I recall), this is when you want to yank the throttle to the lowest point of its throw. This will turn the prop brake ON.
Then, when you're flying in thermals or slope lift, and you pull throttle down to off, the prop brake will engage and your folding props will fold and now your FPV cam will not be obstructed by the prop spinning.
-- courtesy of Pianoman at RCG