To unlock each of Subject 16's videos you need to find the 20 Glyphs around the cities on the buildings and solve the puzzle for them.
Glyphs are symbols that only show up whilst in Eagle Vision (Hold
) once located you need to go near them to begin the sequence, you will be introduced to Glyphs not long after Sequence 1.
The game tells you which building in the game has a Glyph on it by the red eye icon on the picture of the location, you can see a list of locations from the pause menu under 'Database'
Finding the Glyphs is half the battle since you also need to unlock the code for the data by solving the puzzle, they aren't too difficult and if you wait long enough the game will give you the option for a hint. (But I will provide a guide for them below)
Here is a detailed guide on the locations of all 20 Glyphs with pictures of where they are on the map and which part of the building they are on. - Detailed location guide
Here is a guide on solving each puzzle - Puzzle guideAlternatively you can use this puzzle guide as it shows which puzzle goes with which Glyph - Alt puzzle guide
Below is a video of the Glyph location, video credit to rabidkitty4