You really shouldn't have to go through all the steps that kiko mentioned. If you click download at the Store, then select Run, it will download and load into your game automatically. If for some reason it doesn't actually load, look in the Sims 3 Launcher and install it from the Downloads section. Now, when you start a new game, you should see Riverview as a choice in a drop down box. It will be in the same spot where you may have Bridgeport, Twinbrook, or Barnacle Bay.