I'm on OS X too. Here's what you do. Go to: http://members.iinet.net.au/~extreme/ then click on the link to the episodes you want. For example eps 18-23. That then goes to web page with a load of random code in it, just like you said. What you then need to do is copy the URL - that's the web address in the address bar at the top. So for eps 18-23 the URL is http://members.iinet.net.au/~extreme/Seinfeld_e018-023.torrent
Open BitTorrent, go to File and then Open URL and paste that URL in. That should sort you.
You can then repeat this process for other downloads ie you can have more than one Torrent open at any one time. That's usually a good idea cos not all Torrents will have full seeds at any one time so you'll find that some of your Torrents are downloading while others are not. It's also good form to keep the Torrents open even after you've got a 100% download - this enables other users who don't have 100% to download for themselves.