command & conquer 4: tiberian twilight

The "code used" means the game is already registed to an Origin account. I would presume, yours.

Log in to Origin with the account info you initially used to install the game.

Go to your My Games section and download the game.

If your game isn't there you'll have to contact a Game Advisor (accounts) via Live Chat from your computer and check the status of your account.

From the Origin Menu..
Help > Origin Help. Up top next to the Search box

Or..

1 Click on the following link: https://help.ea.com/contact-us
2 Make sure you are logged in (top right corner)
3 Click on the blue button "Contact a Game Advisor"
4 Enter the name of your game or product (or "Origin" for account-related issues) and click "Find Solutions"
5 Select the type of issue and the platform you play on, and click on "Find Solutions".
6 Click on the blue button "I still need help" if the FAQ articles do not apply to your situation.
7 Select a contact option. Note that you may get different contact options depending on your country.