Follow these steps to redeem your Steam Wallet Code:

  1. Sign in to your Steam account in your browser
  2. Go to the Redeem a Steam Wallet Code page
  3. Enter the Steam Wallet Code copied from the "Withdrawals" section in your Idle-Empire User Panel
  4. The funds will be added to your Steam account and be ready for use to buy skins, games, and anything else from Steam!

Note: You can find the official instructions here.