How do you use games dowloaded by bittorrent?

1) If by 'play' you mean it's a video, most torrented videos require the Xvid codec. If you use VLC (http://www.videolan.org/vlc/) the codec is included.

2) If by 'play' you mean game, and the downloaded file is a CD/DVD image (.iso, .nrg, .dda, .mdf, .bin, .cue) you need to mount that image with a CD image mounting program. Free: http://www.daemon-tools.cc/dtcc/download.php?mode=ViewCategory&catid=5

3) If by 'play' you mean you downloaded a .torrent file and don't know what to do with it, http://www.utorrent.com/downloads download micro torrent, and whenever you are downloading a .torrent, choose open with utorrent

after downloading the torrent, just find the location of the torrent and look in the folder for it whatever you downloaded.