Steam Wallet Gift Card activation on Steam Guide

 1- In order to activate your Steam Wallet Gift Card on Steam, first you need to install the Steam Client Application. You can download it here.

2- After you download and launch the app, sign in with your Steam logins, and select ‘View my wallet’ from the drop down menu as showed in the picture below.

3- After you are taken to the Wallet page, select "Redeem a Steam Gift Card or Wallet Code"

4- Copy the Activation Key and paste it in the Steam Wallet Code field, then click ‘Continue’.