This page of the guide to Resident Evil Village will teach you how to put the Charms figurines on your weapons. Additionally, we have included information about how to get rid of unwanted Charms that you may not like after attaching to your weapon.
Charms are otherwise known as weapon ornaments. If you pre-ordered the game, you'll get a Mr. Raccoon Weapon Charm, and if you purchased the Deluxe version or higher, a Mr. Everywhere Weapon Charm.
You can pick the Charms up from trader Duke - he offers them for free. The game will immediately suggest installing them on your weapons.
Charms are attached to gun barrels and, unfortunately, can spoil the immersion a bit with their toy-like appearance. They have no practical use beyond that.
If you don't like the idea of customizing your weapon with a Charm, you can disable the display of ornaments in the game. To do this, you need to go to the game's main menu and under the Special tab set the status to Off for Display Weapon Charms.