I'm not sure if the usual drag and drop will work, if not, open the file and read the readme, it has all the steps you will need.

A remodling of bronze plate helmets to make them look a little more unique.

I've felt that the game's default plate helmets looked a little bland. So I've taken it apon myself to remake every non unique (aka craftable) plate helmet to something other than a square with a face hole or dinky visor. This is the first, taking the barbute-esque bronze helmet and transforming it into a helmet a poor roman soldier would love to have.