@bestwvman - SimCity 3000 is no longer sold by EA in the Origin store, so the best way to find out how to register the game is to go back to the seller for support. If you're installing from a CD, the old CDs for SimCity 3000 will absolutely not run on Windows 10**. They were made with a special kind of copy protection called SecuRom. The only way to run the game now is to get a digital copy. You might want to check GoG.
To add the game to your Origin Game Library: Launch the Origin app > Games > Add Non-Origin Game > browse to the SimCity 3000 program exe
**If you bought the CD used, it's likely that the code was already registered and therefore would not be transferable to your account. Once a game is registered in Origin, the promo code cannot be sold or transferred to another person's account. If this is the case, I would suggest returning to the seller and explaining that you can't use it.
