Effective July 13, 2016, AT&T released a software update for the PRIV™ by BlackBerry® (STV100-1). You can download the update via Firmware Over The Air (FOTA). A Wi-Fi connection is required.
Once downloaded, you can expect the usual Marshmallow goodies, including granular app permissions, adoptable storage, and better battery life thanks to Doze mode.
In any case, if you haven’t yet received an update notification, you can manually check by heading to the “About device” section of your Settings.
Source : androidcentral