In my opinion, the easiest way to add an item to the game is to take an existing item that is in your inventory, and change the Gbid to the new item you want. Choose the affixes you want, and save the changes. As long as the item is an appropriate level (the lvl it first appears in the game or higher) I haven't had any issues yet. If you need help determining the level it starts appearing in the game, use the game guide for items, found here: http://us.battle.net/d3/en/item/
I am also on 360, feel free to add me if you need more help.
I am also on 360, feel free to add me if you need more help.