There are many story missions and tasks you need to complete that require you to hack a drone or a camera in Watch Dogs: Legion. It’s typically better to use an inanimate object to finish up an objective than risking an agent’s life and to photograph evidence; you need to use a specific drone to complete this task. A majority of it, the story-based missions you have to do, will have one of these drones nearby or already available for players.
The particular drone you want to find when required to photograph evidence is the news drone. You should be able to hack it and pilot it to sit in front of whatever objective you need. The news drone is pretty easy to fly, and you can always bring up the controls to display on the bottom of your screen by clicking the right D-pad.
Now, once you find the piece of evidence you need to photograph, it’s a simple matter of clicking down on the D-pad. It’ll bring your view down to a first-person view as the drone, and you can take a picture of whatever evidence you need to photograph. You won’t have to do anything else, as the photograph will make its way to DedSec’s archives. You can only progress forward in certain missions once you have the evidence, so the person leading you through the mission should inform you when you have a useable photograph.