As the first step, we recommend you to verify if your computer and OS meet the requirements. The following link will allow you to get this information.
Regarding your question, keep in mind that you need to install a plug-in in order to get the application working on a proper way. Make sure to follow these recommendations and let us know how it works.
When I go into the watch tab and then click on the setup tab I am directed to a page that tell me my current browser or system is not supported. I am running Vista as well as internet explorer 8 so I am not sure why it is telling me it is not supported. I can watch the slingplayer, the player on the website and well as the mobile player. The only issue I have is I once had the FIOS remote and now I cannot get it back