This page of The Last of Us game guide contains information on where to find the training manuals and tools in the Bus Depot chapter. Those items are collectibles-secrets. Our walkthrough indicates the exact location of each artifact and pendant.
When you get to the platform, examine carefully all of the tents there. Inside the biggest one, there is the toolbox.
Description: Increases the range of explosives.
The manual is inside the truck near the two bloaters.
Climb the cab and collect the manual.