Open the Reason zip folder and then you should see a setup or install file in that folder, open this and then it will open the installer, from what i remember all you need to do then is choose where to install reason to (best to just leave that option as it is, generally just installs to c/program files/propellerhead). This will install reason, once it's complete it will let you know and you will see a reason icon now on your desktop. You should be good to go then.
To be sure, once you've installed reason, go to where you installed it (c/program files/propellerhead/reason) and make sure that the factory sound banks and okestra refill are in there. If they are not then go back to the zip folder you downloaded and they should be in there, just copy them over to your reason folder.