Go to the "Redeem Code" page on Genshin Impact's official website, log in to your account and the site will automatically detect your character and server region. Make sure that the information shown is accurate before you redeem the code.
Alienware is currently giving away limited keys for 50 Primogems. To claim this, you need to log in to your alienware account, or create a new one on their site, and click the "get key" button on the page. Then redeem it on MiHoYo's website. Only 1 key available per account, and you need to be at least Adventure Rank 10 or above to get it. You can't claim this if you redeemed a code from the already expired intel promo code.
This promo does not seem to be officially endorsed/promoted on any of Genshin Impact's official social media, nor is this a promo from GameA.