Download Winrar from their website. It's free and although it makes you think you do, you don't actually have to buy it. from there any .rar file you download it will automatically recognize it.
Once you download Winrar, any .zip folder will automatically turn into a Winrar archive file. It just makes it a more user friendly experience. After you download Winrar download this game (or anything else online really) and when it's done open it up. Inside will be all of the files, decide where to put the files (for games like these they often need to be in the same place or the game wont open because all of its files will be missing) and play the game like normal.