The most likely answer is: in The Forest , you get the yellow crate by finding it in the world and hitting it with a weapon to open it. Yellow crates can contain flares or modern arrows, and known locations include near the cockpit, the Film Crew camp, the Modern Bow location, Cave 6, and the snow biome.

How to open it

  • Equip any weapon.
  • Aim at the ground near the crate and strike it.
  • Once it breaks open, you can collect the loot inside.

What’s inside

  • Flares.
  • Modern arrows.
  • The contents appear to be fixed by the game.

Where people find it

  • Near the cockpit.
  • At the Film Crew camp.
  • Near the Modern Bow location.
  • Cave 6.
  • In the snow biome.

If you meant a different game, tell me which one and I’ll give the exact steps.