This short priority ops becomes available after talking to Kandros and asking him about the APEX strike teams. This unlocks the APEX Strike Missions feature of the game, which requires an internet connection. (Return to the main menu, press square to connect if you’re offline)
This is immediately completed after sending your strike teams to available missions. To make the most out of this feature, I suggest downloading the companion app as well since it allows you to collect the rewards from completed APEX missions,, manage their equipment, redeploy your teams to new missions. You only collect the rewards via the APEX console in The Tempest. This is a good way to earn various resources, credits, and even rare Weapons.