Who wants to be the man?

Alright so I haven't downloaded torrents since I was in high school, and I kind of need a refresher in terms of downloading movies via torrents. I know the whole website deal (pirate bay) etc...But isn't there something I need to download in order to convert the torrent to my Mac? I used to be the master at this type of shit but its been a few years haha. Thanks, any help would be appreciated.