How to activate a Steam Gift Card key?
Redeeming a Steam Gift Card is really easy, just follow these simply steps:
1/ Log into your Steam account or create a new account, and click the "Redeem a Steam Wallet Code" button.
2/ Enter the code that you received into the “Steam Wallet Code” field.
3/ Select Continue.
4/ Subsequently, the denomination value of the gift card will be added to your Steam Wallet. You can see your balance in the upper-right corner of your Steam account.