Put the plugin into the plugin folder and you're good to go. To reset the vault, simply use the matching trial key on the vault to reset it (Doesn't consume the key). Once reset, players can use their key to open the vault again and consumes the key. This works for regular vaults and ominous vaults.

Requires Rtag plugin dependency:
https://www.spigotmc.org/resources/rtag-api-to-edit-block-entity-item-nbt-1-8-8-1-21.100694/