In-game redemption:
1. Log in to Honkai: Star Rail and click on the Phone menu in the top left corner.
2. Tap on the "..." button at the top right corner.
3. Click on "Redemption Code".
4. Enter your Redemption Code and click "Confirm".
Website redemption:
1. Go to the HSR website. Click on the "More" button at the top bar and select "Redemption Code".
2. To select a server, log in to your HoYoverse Account and follow the instructions on the screen.
3. Enter your Redemption Code and click on the "Redeem" button.
*After redeeming a code, you will receive the redeemed items via in-game mail.
*Make sure to unlock the Mailbox function by completing the Trailblaze Mission "The Blue" - "A Moment of Peace" in the game and claim your rewards. The mail will expire after 30 days, so don't forget to claim the rewards.