How do I redeem my iTunes gift card?

Open iTunes.
Under the "STORE" header on the left, click on "iTunes Store." Then under "QUICK LINKS" on the right hand side, the top option is "Redeem."

Tried that, still cannot redeem it.

What happens when you try to redeem it?

B-rock

The activation code does not work, says invalid code. Spoke to an apple tech who could not help. This $50'card is a loss. Apple does not refund the card.

See here: iTunes Store: Invalid, inactive, or illegible codes

B-rock

http://support.apple.com/kb/HT1574

i won a contest from a game and the prize is itunes gift card. the gift card was from US store but i make my apple id here in China. how can i redeem the card?