Dress Your Companion
Early in the game, you'll meet a dog called Dogmeat. Dogmeat is just one of the companions you'll be able to deploy alongside your character in your journey.
One thing that Bethesda fails to outline in detail when you get Dogmeat (and your other companions) is that you can outfit them with their own set of gear. For instance, I've clothed Dogmeat in some armor with a pair of goggles. Here's how to do this.
Open up a trade with Dogmeat or Codsworth or whomever is following you. Trade them. If the item is equippable, an Equip option will appear on screen. Equip the item and you're good to go.