I know this is long overdue but just in case someone is having the same problem (as was I today until I figured it out), the way you do it on Origin, click you Sims 3 game as if you're going to play it but then click more and then EP and from there you can install the EPs. They provide you with the product code of which you need to copy and paste.
Hope that helped !
Where are you seeing the codes? I’ve been super frustrated because I’m trying to add the island paradise EP to my game but can’t find the code anywhere. I’m able to “download” the game but get stopped because I need the registration code that I don’t have (and isn’t in the confirmation email).
