You download a bit torrent program, then click on the torrent you want to download...the trick is there has to be Seeders(people who have the show and are letting you download it from them). The higher the number of seeders, the faster it will download. Some sites will list torrents that only have leeches (people like you who don't have the show but want it) I'm guessing that some GRAB shows on Etree at this point only have leeches. And don't try a torrent that only has one or two seeders, because if they decide to turn off their computer, you will be stuck. I have multiple torrents stuck at 45% complete and whatnot.
You will also need to download a flac program and an MKW Audio compression program, so you can extract the music files once the torrent downloads.
If you want the best GRAB show, get the one from Cleveland....its available for $10 on livephish.com, and its soundboard quality...highlights include a kick ass Billy Jean Jam (yes, Micheal Jackson's Billy Jean) and an accoustic/bluegrass Wilson. I was there, so I might be a little partial, but from what other reviewers have said, that is the best show of last summers tour.