This is achieved by completing the side mission
Lamb to the Slaughter. It's the last side mission that you will get, so it'll be quite late into the story.
To avoid spoilers, I'll just suggest that you check on Jack Ryder in the GCPD Interview Room, every time the main story requires you to go to GCPD. You'll know it's the right time when he isn't there, and you have a tape to listen to instead, which will begin the side mission.
It consists of a single, very simple mission that will offer no real challenge. But 3 upgrade points, so yay!
EDIT: It turns out that listening to Ryder's tape is not the only way to start this mission, as once you complete your next small objective of the main story, it will automatically be triggered.
For anyone annoyed by my vagueness, I've added some more concise but spoiler adjacent info below.
*** Spoiler - click to reveal ***Jack Ryder will be missing, and the tape that starts the mission there when you are told to go to the GCPD just after finding out the Arkham Knight's identity. This happens at roughly 85% completion of the main story. If you don't listen to the tape, the mission is automatically started after bringing the Clocktower servers back online, which is your next objective after leaving GCPD.