You have to unlock it. It’s only on per default in games that were tested with pos tracking. On the head tracking page of the ingame menu is an according option.
Once unlocked you also get controls to adjust pos sensitivity, but the auto detection is usually quite good. So probably you won’t have to touch those.
alright, took me a little while, but for anyone else that might come across this in the future, expert settings has to be on in order to see the positional tracking option on the in-game menu