Follow these steps to redeem your Skype Prepaid Card

  1. Sign in to your Skype account in your browser
  2. Go to the Redeem Your Card page
  3. Enter the Skype Prepaid Card which you can find under My Withdrawals by clicking on "Show Code"
  4. The Skype Credits have now been added to your Skype account

Note: You can find the official instructions here.