Did you register it before ? If so, there's no need to do it again.
Login with the account you've registered the games on and find them in myGames on the Origin client to download.
If you never registered, you need to get in touch with a customer support game advisor
Game advisors can be found through live chat.
- https://help.ea.com/en/contact-us/
- Set your language to US at the bottom
- Click on Contact a game advisor
- Describe your issue with a few words
- Click on Find a Solution
- Select Product: ex: The Sims 3 or Origin
- Select Issue Type: ex: Billing/Purchasing or Account Management
- Select Platform: PC
- Click Find solution
- Scroll down and click I still need help
- Click Chat Now to chat with a Game Advisor
With Pics here: http://sims3.crinrict.com/en/2012/10/how-to-contact-ea.html