You can redeem active redemption codes in Genshin Impact on the game's official website or in-game, it's up to you which is more convenient for you. If you decide to use the website, you'll need to login using your HoYoverse account and select your server. You can then enter any of the active redemption codes listed above in the appropriate text field. You should subsequently get a notification confirming your redemption was successful.
If you choose to do it in-game on PS5 or PS4, then you need to bring up the main Paimon menu using the Options button. From there select Settings > Account > Redeem Code. You can then type out any of the above active redemption codes in the text box that appears. Whichever method you adopt, you'll find your rewards delivered directly to your game's built-in Mailbox, which is accessed from the Paimon menu.