Yup you can install from the dashboard. ratchie is correct, at times it can take forever. Usually I only have an item or 2 that make it go slow, then it goes at a nice pace. It shows you what you have installed and what is not installed.
A thing I forgot to mention, is make sure you are logged in. Either from the launcher or through the in-game store screen. Worlds, hair, and clothes take the longest to install from the dashboard. Furniture and other items not so long.
If it does show that Riverview is installed but it is not an option to start a game in. I would un-install it and try it again. I know others have had problems with Riverview, though I am not sure what process was taken to fix it.