Yeah, I'm having the same problem here (except I didn't waste my money on the game), but I don't know what program to use either. I tried opening it with the 3viewer, but it didn't really do anything...
You have to open the program first, then open the file you want to install from inside the program. The big button with a 3 on it is the install button. The first time you open it, you have to configure it to your installation, but it'll choose the default installation first.
I use it because it's the only program I've found so far that works on macs, and because the launcher recently started having problems installing things (after weeks of working fine). I'm wondering if installing Riverview screwed it up, though, since that was the only new addition to the game prior to the screwiness.