The first step is to open the App Store on the desktop;

The second step is to click on the avatar in the upper right corner to enter the account page.

The third step is to click Redeem Gift Card or Code to enter the redemption page.

The fourth step, if it is a physical recharge card, you can click "use camera" to scan it. If it is an electronic recharge card, just click "Enter Code Manually" below to enter it.