I have Sims 3 on Steam. I want to play Roaring Heights how do I download it?

@slothincloud24  First, make sure your CD key for the base game is registered to your EA account.  You can add it on www.thesims3.com rather than using the EA App, and in fact that's worth doing just to confirm that you have an active account on that website.

Rather than using the EA App, buy Roaring Heights from the website:

https://www.ea.com/games/the-sims/the-sims-3/the-sims-3-roaring-heights/buy-microcontent

You'll receive a confirmation email with a product code included.  Register that code on the same Sims 3 site, and download it from there, either from your purchase history (Store > My Store Account > Purchase History) or from its product page.

https://store.thesims3.com/roaringheights.html?categoryId=12642

You don't need to use the EA App at all, and the product code won't work in Steam.  Store worlds can only be installed through the Store site.

For more information about registering and installing Store worlds, please see the first post of this thread:

https://answers.ea.com/t5/Store-Issues/Sims-3-Store-world-can-t-register-install/td-p/12619800