It’s pretty simple- you will get this as you go through the campaign or a little bit after you beat it. Watch out for blue question marks in the map, as they count as a collectible. The “radio free Oregon” broadcast will come on every now and then while riding your bike, and if you listen all the way through, it will count as a collectible. Keep a lookout for character collectibles, which are generally scattered around camps. NERO recorders are found at NERO checkpoints and research sites. There are also historical landmarks, which have their own marker in the map. If you keep finding these, you will get this and the trophy for finding over 75% of collectibles.