After you've placed the order, we assign a PRO player with X-51 Nether-Rocket item in his inventory. He works according to the agreed schedule and will contact you in-game to trade you X-51 Nether-Rocket.
As soon as you receive X-51 Nether-Rocket you can learn it from your inventory, and it will become available to all the characters on your account. If X-51 Nether-Rocket is the Blizzcon promotion code, you will receive a digital code to redeem at your battle.net account page.