Hello ,
Thank you for posting in the community and at this time Promo codes should be redeemed before March 31 2022 to make sure you get the Twinmotion commercial version when you receive the computer. The Promo codes have expiration dates so it won't work if you wait after the specified date.
You can create an Epic Games Account and redeem the promo code, once you receive your new computer you will be able to download the Epic Games launcher and sign-in with the account you created and start download/installing Twinmotion.
Here is the link to download the Epic Games launcher:
https://www.twinmotion.com/download
Hope this makes sense and if you have any follow-up questions please let us know.
Kind regards,
Vincent B.