Does any one know when pre load is available on Series consoles?

I have tried and tried but I cannot find a way to pre load campaign on Xbox, yet I’m hearing reports it works fine on the Windows Store on PC. Are MS really going to make everyone wait until peak times and then have to download it all at once? As far as I can find 343i haven’t addressed this even once and the game is out in 27 hours. Any help would be appreciated!