In Warlords of Draenor, this item will be added to the new Toy Box feature and no longer take up a bag slot. You will be able to "use" the item straight from the Toy Box interface.
The Toy Box will be account-wide and therefore so will this item.
Carved Ogre Idol is a World of Warcraft: TCG item that was obtainable by collecting and using UDE (Upper Deck Entertainment) Points. UDE lost the license to create and sell cards for the WoW TCG in 2010 - Cryptozoic acquired the license later on - so the only possible means of procuring the item is to buy it. This is not for the faint of heart; the rarity of the loot card makes it worth hundreds of dollars.
For more information, see Carved Ogre Idol on wowtcgloot.com and wowpedia.org.
For redeeming the 25-digit code, visit the WoW Promotion page. Follow its instructions and use the new, in-game code with Landro Longshot.