Forum Discussion
@owlinabasket In general, Sims 4 product codes need to be redeemed in Origin, or now in the EA App for Windows users. If you've installed the base game through Steam, you could then download your packs through the EA App, and the data would go into the Steam install's program files and load in-game just as if you'd bought it through Steam.
However, in this case, you can't register this pack at all. Each product code can only be used once, and there's no way to free up a used code even if the original owner doesn't want it anymore. If you want the pack, you'll need to buy it yourself.
Both Steam and the EA App have frequent sales of Sims 4 content, with expansion packs usually 50% off. That's not as cheap as $10, but it's better than $40.