Well, you have to use WinRAR program (for Windows users). Make sure you have it in your PC...if not, download it as a shareprogram. Then, you have to open WinRAR icon with the contents, extract the files you have downloaded somwhere onto the hard disk in your PC and the typical installation window should appear just after.
Cheers
WinRAR looks like something that has to be purchased. Is there no freeware availble that will open these things?