This plugin loads custom items from the "Items" subfolder. Every item has to be in a separate subfolder which contains an "ItemDefinition.txt" file (see baseball bat example item) as well as the item model (.obj), icon (.dds, .png or .jpg) and texture (.dds, .png or .jpg). 
You also find an "AnimationList.txt" file in this plugin folder which contains a list of all animations which can be used for your custom items.