Open the .torrent file with uTorrent / BitTorrent, wait until it finishes downloading. Then get Alcohol 120% or Daemon Tools and check the settings so you have that 1 image or whatever that thing is (just use common sense). Then press mount button somewhere (you can find it easily with daemon tools) and search for the .iso file. Mount the .iso file and then if it doesn't automatically open, then go to My Computer and double-click the E: folder or something like that (the name of it depends on some stuff that I don't know about) and then run setup.exe or autorun.exe.
If it's movie etc, then just find the folder where it got downloaded to and watch it (the folder is in either C:/ or My Documents and it's named Downloads).