It is little hard to add items and run the plugin if you don't understand sql. You can check the csitems.sql to see the structure.
Code:
INSERT INTO `items` (`id`, `name`, `type`, `armor`, `health`, `magicfind`, `quality`, `speed`, `jump`) VALUES
(1, 'None', 'None', 0, 0, 0, 0, 0, 0);
You replace the the values in order to create your own item, the id have to be uniqe and after you have to make sql request.