1Go to https://store.steampowered.com/account/redeemwalletcode and sign in if you aren't already.
2You will need to create a Steam account if you do not already have one.
3Once logged into Steam, click on your username at the top-right corner and select "Account details."
4Click "Add funds to your Steam Wallet" and then "Redeem a Steam Gift Card or Wallet Code."
5Type in the code from your gift card and click "Continue."
6Follow the instructions to add the funds to your Steam Wallet.
7Note: If you have never used Steam Wallet credit on your account, you may be prompted to enter your current address to determine the correct currency.
8The value of the Steam Wallet code will be added to your account's Steam Wallet balance. The current available balance will be listed in the upper right-hand corner below your profile.
