Hello,
As some of you may know, Game Packs are a new format introduced by EA/Maxis. At the moment, they are downloadable only. However, when you purchase it, you may not know how to download it. Hopefully this will help you in that instance
Can't Download It?If you have trouble downloading the Game Pack, go to My Games > The Sims 4 in Origin and try clicking the little "i" (more details) as in the screenshot below. This will take you to a page where you can manage the Game Packs you own. We're hoping EA makes this a little more obvious for the future, else we'll see a lot of confused players.