There is a code that came in your physical box that on the front said something about Sims Social. I heard it was red in color and on the back it has a 16 alphanumerical code that needs to be put in against your account on the Sims 3 website. You register your game with your account and then go to the Sims 3 store and go to my account. One of the options should be Redeem a Code. Just like if you've received the birthday package from Sims 3.
As for the items - I'll get back to you as soon as my game has loaded.
Edit: The items can be bought in buydebug but not regular buy mode. The register is available under community lot objects in build mode. Here is a shot of the store and a shot of all the things you can buy from it that's exclusive to the store.
A bed, rug, cat hiding spot, scratch post, doghouse, 2 store signs, a window, a door and Regal racing posts.