The listing, Xbox Live Gold 48 Hour has ended.
To redeem
1. Sign in to XBOX LIVE account (the one on which you want use this code on)
2. Press central (Guide) button on controller.
3. Go to Marketplace blade and on this blade choose "Redeem Code" option.
4. Enter received 25 digit code and hit the confirm button.
5. On next screen choose confirm.
Also sometimes on the console you need to reset your status because even though you redeemed your code it will still say you are not a gold member.
Reset status
1.Go to settings and press A on system.
2.Go to Network Settings and choose wired or wireless, whatever it is you have.
3.Test Xbox live Connection and wait till it tests.
4.When done testing sign back into your account and your ready for the Xbox live gold experience, and enjoy.