Use the drag ann drop zones in the C menu to quickly interact with your inventory, holster your weapon by using the chat command instead of having to drop and pick it up into your inventory and more!
This is very important as the script won't work without it. Once this is added to your collection, you can simply drag the xenin_inventory folder into your Garry's Mod addons folder. The configuration files can be found in /addons/inventory/lua/inventory/configuration/. The main configuration file is config.lua.