walk over to the defender and stand next to them. Go into your inventory and select the item you want to drop, be it a weapon, bullets or anything else that you might want to give to a defender. The controls wil be listed at the bottom of the screen and you will see an option down there to drop the item. It will be the right stick on consoles anyway. Once you drop the item near a defender, they will pick it up and start using it.
